Help with Magus Build

[Smite Neutral]

I am starting a new campaign, not pfs, and one of my fellow players is new to pathfinder and wants my help with his build. He wants to play a tiefling magus, with a dex-based melee style. I have no experience with the class, and all I know about dex-based melee is that he needs weapon finesse at lvl 1 and then either the agile weapon property or the dervish dancer feat.

I know about the magical lineage trait with shocking grasp so it can be intensified at level 7, or level 6 with feat retraining. I also know that wayang spellhunter does the same thing and that while cheesy he could take both naming shocking grasp, and then abuse quicken/maximize.

My question is what should this build look like up to level 7 or so? Is there any advice I should give him? What is mandatory for this kind of build? I still don't quite get how the class works entirely. How does he deal with concentration checks while using spell combat and spellstrike? Combat casting and focused mind feel like a waste of resources. Lunge seems promising but comes online late.

So far I've got

Base tiefling (+2 dex, +2 int, -2 cha). the alternate racial traits didnt seem very useful
Base magus. I havent checked out the archetypes but may read through them.

Traits: magical lineage and ?

Feats:
1-weapon finesse with a rapier
3-either dervish dancer, or he waits until he can afford agile, or he retrains out of dervish dancer when he can afford agile, his choice

[Greeeit]

I think you've got the most important stuff down. Dervish is probably going to be a better choice, as the agile weapon would require you to get the price equivalent of a +2 weapon (off the top of my head an 8000gp investment, and your wealth by level is expected around 3000gp at lvl 3 where you would be getting dervish dancer).

Spellcombat gives you a full round attack and then a spell (or two if you can cast quicken spell), while taking a -2 on attack rolls. You can also take extra penalties to attack to get bonuses on concentration. Defensive casting is a bit of a pain early on, but gets better as you level, so you should be able to manage without spending feats on concentration.

You'll probably be wanting to get arcane accuracy to make up for the magus' 3/4 bab, but other than that you're free to customize. Personally I like getting preferred spell (lets you spontaneously cast a spell of your choice) as it gives you room to get utility spells instead of filling all your slots with shocking grasp.

[Kifaru]

I like to take the Wand Wielder arcana at level 3 and stock up on cheap wands. This allows you to cast something every round. My two favorites are Blade Lash and True Strike.

[avr]

Once he has mirror image up, or even just shield, it can be worth simply taking the AoO rather than casting defensively. If possible though he should arrange things so that he can cast then 5' step into attack with spell combat, or cast normally & move (then deliver an attack if the spell cast was a touch attack spell). Also using wands doesn't provoke AoOs so if he uses Kifaru's plan that makes it easier.

Empower is usually better value than maximize & it becomes useful earlier. In most games I'd take one of the magic item crafting feats fairly early; if using wands a lot probably craft wand, otherwise craft wondrous item most likely.

Besides wand wielder some other useful low level magus arcana are arcane accuracy or prescient attack, familiar, or flamboyant arcana. Maybe spell shield.

[Matt2VK]

Depending on your game and how fast you level, you might want to warn him that DEX based magus have lousy damage till around 3+ levels. When you're able to get that DEX to damage added into your melee attacks and your shocking grasp starts doing reasonable damage.

Then there's the question of "How magic heavy is your game?"
Will your GM allow purchase of low level potions and wands when you want them?
If so, suggest you have the Tiefling get the racial: Prehensile Tail in place of Fiendish Sorcery. This gives the tiefling a 'extra' hand for grabbing wands and potions.

[blashimov]

My recommendation is black blade and hexcrafter archetypes.
You level faster than your spells do, so concentration checks should get doable. They are not avoidable entirely, however.

Focused mind is nice because it assists with all concentration checks, so I recommend it.

As for how the build works at most levels:
Start of combat:
swift action enhance your sword from your arcane pool
cast shocking grasp
move to melee
take your free attack with spell strike

if someone is in your face already: attack 5ft back and cast shield or buff

further rounds:
cast shocking grasp
attack twice at -2 to hit for spell combat
the first attack that hits discharges shocking grasp

Other fun combos:
bladed dash or force hook charge ending your move next to someone, take your spell combat extra attack.