I'm not able to help you create a build (although I'm sure you'll get other volunteers on this forum), but if you want to just see options from the Core Rulebook, I recommend the legacy version of 1E PRD that Paizo used to maintain. On the menu to the left, expand "Core Rulebook" to expand and see only options from the 1E Core Rulebook
Well until you hit level 4 you could try a scythe on a normal hit you deal 2d4 and on a critical hit you deal 8d4. you could combine this with the intimidate skill to demoralise enemy.Add on some Druid spells like entangle and you should be fine. Make sure to wear the best armour possible. I will say this is advice come from a multitude of different Druids using these against me.
Goldcape
My advice for a melee-focused half-orc druid that will transition to wild-shape, using only the Core Rulebook:
1) Prioritize Str/Wis, then Dex/Con for ability scores. You can probably start with a slightly higher Str than Wis (instead of emphasizing Wis only, as with a caster-focused druid) and plan most of your advancements in Wis to keep up with your spell slots (19-20+ Wis at 16th-20th level). You will want at least a mid-range Dex and Con for AC in medium armor (likely a dragonhide breastplate when you can afford it, +5 AC, +3 max Dex; eventually with an ioun stone [deep red sphere]) and a 12-14+ Con for additional hit points (useful for a melee-focused character).
2) Start planning for wild shape early. You will want Eschew Materials as your feat at 1st or 3rd level (probably at 1st; see next item) and Natural Spell as your feat at 5th level to cast while in wild shape; Eschew Materials to cast without material components (unless costly) and Natural Spell to cast using animal noises/movements in place of the normal verbal and somatic components.
3) Half-orcs gain proficiency in greataxes and falchions from Weapon Familiarity, so a melee-focused half-orc druid can use a falchion (2d4 S, 18-20/x2) as their primary weapon when not in wild shape. For combat with two-handed melee weapons, as well as primary natural attacks in wild shape, Power Attack is very useful; because it has a +1 BAB prerequisite, a druid will have to wait until 3rd level to take it but it is almost definitely worth it.
4) For Nature Bond, you may want to consider the Animal Domain to gain the bonus domain spells and abilities as well as a slightly less powerful animal companion at 4th level (as druid level -3) instead of choosing an animal companion by itself; you mentioned Core Rulebook only, but you may want to check and see if the GM will allow the feat Boon Companion anyway (if so, taking the Animal Domain is a no-brainer, IMO).
Eschew Materials is not needed if you have Natural Spell. Natural Spell allows you to use any material components or focuses you possess even when in Wild Shape.
Using only the core rule book is going to simplify your build because it removes so many options. Your spell list and feats available are a fraction of what the full game has. My copy of Hero Lab lists well over a hundred 1st level druid spells, the core rule book has less than 20.
I would recommend against using the animal domain. The first three spells you gain from it are only good at controlling animals. The next two spells are duplicated by class abilities. This means until 11th level the spells are at best marginally useful in most campaigns. If your campaign is focused on surviving in the wilderness the first three spells might be more useful. Most of the other available domains are going to be more useful for a caster focused druid. I would stick with the animal companion for the nature bond.
Considering your smaller spell list and the fact Druids can spontaneously cast summon Nature’s Ally focusing on summoning is a good route. Augment Summoning is in the core rule book. Take Spell Focus Conjuration at 1st level, Augment Summoning at 3rd and Natural Spell at 5th. After that there is not much that really stands out for feats.
For stats I would probably try and get 14 in STR, DEX, CON and 17-18 is WIS (including Racial bonus). If you are using a 20pt buy dump CHA to 8 to get 17 WIS, on a 25pt buy you can get a 18 WIS without dumping CHA.
After that you can focus on general combat feats like dodge, toughness, lightning reflexes to boost your defenses. I know this may seem like a bare bones build, but with only the core rule book there are not a lot of options.
Spell Focus Conjuration is the requirement to take Augment Summoning. If you don't want to summon anything, you don't have to take it if you don't want to. Especially since you'll need Sacred Summons to cut the time the summon spell takes so you can do other things during your turn.
A big cat or a Deinonychus (it's a dino) are decent choices. They both get multiple natural attacks and then pounce at level 7. The dino has a few more attacks and a greater speed. The cat gets rake and grab and is bigger.
You may want to consider starting with 16 Str (14 +2), 14 Dex, 13 Con, 8 Int, 15 Wis, 7 Cha (or even 14 Con, 7 Int) using 15-point buy and investing in a headband of inspired wisdom ASAP. With all of your advancements in Wis and a headband of inspired wisdom +6, you will still have an effective 26 Wis (+8 bonus) at 20th level (vs. 27 Wis for starting at 16) and be better at melee combat both in wild shape and out.
Effectively, you are trading a -1 on Wis bonus for half your levels for a +1 on Str bonus for all your levels.
It depends on what YOU want to do. If you plan to go into melee, Power Attack is always good. If you're going with wildshape and natural weapons, I'd avoid Weapon Focus unless EITR is in use.
What is EITR ?
Elephant In The Room, a popular set of home rules that likely wont come up since your GM is going Core only.
Is putting one level in monk a good idea ? Is deluge of blow working when i'm in wildshape ?
Flurry of blows does not work with your natural attack when in wild shape, it's one or the other.
I would recommend going with dragonchess's stat array.
For feats I would say go either combat reflexes or toughness for 1st level, power attack for 3rd level, and natural spell for 5th level.
An animal companion will probably be better since you're focused on fighting more than casting. Big cat will have a higher str score and grab, deinonychus will have more attacks and hp. Up to you which one to use. Maybe ask your GM for advice about which one would fit the campaign better.
Until you get to level 4, since you're a half-orc, you have the option to use a greataxe which is pretty good. If you took combat reflexes, you can opt to use a longspear instead to take advantage of reach.
Speaking of being a half-orc, always prepare at least one Cure X Wounds spell. If you get knocked into negatives, you can use Orc Ferocity for one last standard action before going unconscious, which is enough to 5' step and use healing on yourself. If you get back into positive hp you even get to act normally again. Just remind the rest of the party that you're not a walking bandaid dispenser, you're emergency healing. That said, an economical purchase for every party is wands of cure light wounds to heal up between fights.
Other useful buff spells to keep in mind later on will be barkskin (lasts 10 minutes per caster level, you can pop it on right before heading into the dungeon and it should last the whole time) and magic fang/greater magic fang to give you damage bonuses on your natural attacks (you might need to transform first before casting these, ask your GM. If not, cast greater magic fang when setting out in the morning since it lasts HOURS per caster level). If you get lost in the wilderness, goodberry, create water, and endure elements will make survival trivial. Detect magic is also always useful to have since it's free and can be cast indefinitely.
Thankfully, you're a prepared caster, so you can change your spell selection every day to whatever is most useful in that situation. Just keep in mind that if you want to cast a spell multiple times per day then you have to prepare it multiple times.
One thing to keep in mind is that a druid is a full 9th level caster whit a medium BAB. Spells are a big part of the class and melee combat even with Wild Shape is not going to be as good as a full marital class. Being limited to the core rule book only eliminates a lot of the better options for your concept. Using a 15-point buy is going to make it even harder to do multiple things well. Most games I have seen use at least a 20-point buy.
If you ignore your spells, you are ignoring the most powerful aspect of your class. At minimum you need a WIS high enough to cast your spells. That means by 7th level you need a 14, 9th will need a 15, 11th needs th needs 17, 15th needs an 18, and 17th needs a 19. You get 4 stat increases that can be used to raise your stats to the required number. Technically you get 5 but the 5th one is at 20th level so by that may not be soon enough. Normally you can count on stat boosting items to raise up your stats, but this campaign seems to have a lot of restrictions so I am not sure I would count on a headband being available when you need it. Starting with less than a 14 WIS means you are going to delay access to some of your spell levels if you cannot secure a headband. The other thing to look at is how high level will the character reach? If you are not going past 12th level, you don’t need to worry about 7th level spells. If the campaign goes to 20 you are going you are going to want at least a 19 WIS.
In addition to determining what spells, you can cast WIS also affects the saving throws of your spells. This is the reason most casters max out their casting stat. If you are splitting your focus the only way to do that is to sacrifice some WIS, which means your offensive spells will usually be less effective. The way to minimize this is to focus on spells that do not have saving throw. The good news is Druids do have a decent number of offensive spells that do not get saving throw. But this will cut down on the number of viable spells you have access to. Entangle is one of the best 1st level druid's spells, but it does get a saving throw so may not be as effective for you.
One type of spell that does not get saving throws are summons. That is one of the reasons I suggested focusing on summon natures ally spells. That and the fact that a druid can spontaneously cast them, so they never have to memorize them. This allows you to memorize other spells but be able to use that slot for a summon natures ally spell. Essentially that gives you two choices for every spell slot. You can cast the memorized spell, or you can cast a summon natures ally spell. Since summoning is always an option for a druid focusing on summoning is very effective.
If you do want to focus on combat, I would recommend the following stats STR 16(including +2 racial from half orc), DEX 14, CON 14, INT 9, WIS 14, CHA 7. Dropping the INT to 8 gives you an extra point but nowhere to spend it. If you are able to secure a headband you can increase STR as you level up, but if you cannot put it into WIS to get access to your spells.
If you are starting at 1st level use a great axe instead of a falchion. The great axe is a lot cheaper so that will allow you to also pick up better armor.
Power Attack is something I would be careful about. Druids lower BAB and the fact your STR is probably going to be lower than a full marital means your chance of hitting with power attack.
Last thing I would mention is that this character is never going to match a full marital class in combat. You should be able to contribute in combat and will probably have more out of combat utility, but the full martial is going to be better at fighting. Having an animal companion will bring you up to nearly par but the character himself will always be slightly behind.