Hunter was one of the later classes I tried in OB, so I only got to level 9 or 10. Ammo is dirt cheap at the lower levels at least. After killing a few creatures and selling the loot, I was able to fill up my ammo bag with no trouble. Ammo is sold in stacks of 200, and you can fit 6 stacks (I think) in the ammo bag you start with. You can put more ammo in regular bags, but the ammo bag gives an increase to shooting speed. I'm going to train in mining and engineering so I can make my own ammo among other things.