Adamant is still a decent nature for it, although Jolly is probably better. However, what ability does it have? Technician and Skill Link are fine, but Pickup is useless competitively. However, thanks to the new Ability Capsule you can change its nature to Technician if it isn't already.
So try a move set like this:
Ambipom @ Life Orb
Trait: Technician
Nature: Adamant
EV's: 252 Att/252 Spd/4 Def
Moves:
-Fake Out
- Aerial Ace
- Payback
- Power-up Punch/Low Sweep
This is pretty close to Smogon's Jolly-Life-Orb move set, but I tweaked it a bit mainly because of personal preference than for anything else. Fake Out gets STAB, Technician boost, and priority. Aerial Ace deals with Fighting types (especially Heracross). Payback is for the Ghosts that would otherwise wall this thing completely. Shadow Claw can be used instead, but doesn't get the added bonus from Technician. Payback has the added bonus of doubling in power if Ambipom is hit first, so that is a handy bonus. The last slot is a choice of Fighting type moves. Power-up Punch boosts your Attack even further, and will also do decent damage thanks to Technician. Low Sweep is more powerful (and still Technician boosted), and lowers the target's Speed, which could be very useful for your not-Jolly (Jollyless?) Ambipom.
As for how much not being Jolly will affect its usefulness, it is hard to tell. It is Jolly in Smogon's Gen V movesets, probably to make sure it outspeeds potential threats like Virizion (base 108 speed). This speed is important because of its horrible defences - it really can't afford to take many hits. However, we don't really know how the tiers are going to be for X and Y (although we can certainly speculate), so it is hard to say. My advice would be to try the set I gave above, and if you are finding lack of Speed to be a problem, then change up its move set a bit and give it a Choice Scarf.
