When levelling a character use the following formula to determine hit points:
(Hit Dice total / 2) + ( Roll / 2 )
This should give you at least half the hit dice + 1 health per level.
Ammunition and Spell Components
These are effectively free and unlimited. Enhanced arrows however must be accounted for.
I’m allowing this just to speed up the game and saying that at some point while in town you restock up on components and you are going and retrieving your arrows from corpses.