Making a 3/4 BAB d8 hit die light armor class with no inherent bonuses to hit or to AC into a front line combatant is a pretty tricky affair - just ask your nearest Rogue. Still, you do have options.
Option 1: Strength based. Try to get up to an 18 strength and pick up your simple weapon of choice. Get Power Attack and Arcane Strike and you'll be dealing pretty reasonable damage... when you hit, that is. You'll need as many bonuses to to-hit as you can get: flanking, bull's strength, etc. Make sure you pick up Haste as a level 2 spell - it will more than double your damage output on full attacks and give you other bonuses besides. Your AC won't be great, so bolster it with Shield and enchanted armor, and consider spells like Blur and Displacement. MINIMUM CONSTITUTION 14! (Charisma isn't terribly important here; stay away from spells with saves.) Keep a longspear and some javelins handy to increase your range - using a lonsgpear with Enlarge Person to have a 20 foot reach is always fun.
Option 2: Dex based. This will require an Agile weapon or Dervish Dance to work, don't bother if you can't get one of those two. Keep in mind you don't have Scimitar proficiency naturally - a human or half-elf can pick it up at 1st level as a bonus feat, or you can use the trait Heirloom Weapon and be less effective than a limp biscuit if it gets sundered. Your damage will suffer considerably compared to a strength-based character, even with Arcane Strike, but your AC and skills will be better, you'll be less MAD, and it opens up small races like Halfling and Gnome.
As for the Eidolon... well, feel free to go crazy with it. You can totally change the evolutions every level, so take your preferred movement, senses, and Skilled evolutions. Giving it a Bite with Trip and possibly Reach and Poison can make it quite a nuisance in combat. Improved Natural Armor and energy resistances are good, but not essential, since if it dies in combat it just comes back the next day. I'd probably go Quadruped or Biped, but there's really no wrong way to go here. You may consider teamwork feats like Outflank, but for a real laugh, get your DM to approve an Eidolon with Antagonize.