
Third Mind |

For Synth you definitely want half-elf, alternate favored class bonus and immunity to sleep effects means a whole lot.
As for feats, you'd probably want at the very least to have weapon focus: (natural weapon of choice) because hitting tends to be useful. Power Attack when you can get it for the damage. I've seen it both ways on Extra Evolution, whether you can take it or not that is. I recall seeing someone post something saying you can. Maybe some combat maneuver feats if you intend to use them.
A side note: If you're not stuck on biped, I would suggest quadruped instead as pounce is a big thing to give up.

Third Mind |

Well, the only natural attack you have to have with quad is bite, because that is what it starts you out with. Outside of that, you can focus on claws as much as you can and please and don't have to get any of the others if you do not wish to do so. However, you do have to stick within your attack limit. I.e. the number listed in the eidolon section.

cnetarian |
evolutions for a quadruped:
- 3 evolution points claws (on legs), pounce, 1 point free
- 4 revolution points claws (leg), pounce, limbs (arms) (yay spells)
- 5 evolution points claws (leg), (limbs arms), claws (arms), pounce
with 3 or 4 evolution points your attacks are bite + claw + claw, with 5 evolution points you can shift to all claws (don't use the bite and specialize), if you don't mind wearing an eidolon having 4 legs and 6 arms you can make all of your attacks claws.
You could take limbs (arms) at level 1 and cast spells or use weapons, if you want to forgo pounce (and the free evolution point) at level 1, but isn't pounce why you chose a quadruped?

iammercy |

Just thought I would throw out something silly. It won't come into it's own until 11th level but when it does.. well.
Feats:
1 - Extra evolution
3 - Weapon Focus: Claws
5 - Extra evolution
7 - Dimensional Agility
9 - Dimensional Assault
11 - Dimensional Dervish
At 11th level you have 6 (you have a 24 Cha by now yes?) 3rd level spells (Dimension Door) and 1 from Maker's Jump a day.
So 7 times a day you can effectively blink around the battlefield putting out your attacks however you like.
Evolutions:
Limbs (arms x 2) = 4pts
Claws (x2) = 2pts
Large = 4pts
Leaving you with 9 evolution points to dump into Immunity, Armor, Stat increases, or whatever else you like.