Obtaining and Using Weapons and Items
Obviously you obtain weapons and items by buying them. Simple enough. Now, using them.
Everyone starts with the same weapon; the VP70 Pistol. You can do any of the moves with this that you have learned that are listed in it's attack category. For example, hand to hand combat (punches, kicks, etc.) are all Lv.1. Small arms (pistols) are Lv.3. All moves are designated with a level. If you learn a move that is a Lv.3, you can use it because you have a Lv.3 weapon (the VP70). Likewise, you can use any moves that are Lv.1 you can perform because they use your hands, feet, and other appendages. This does not mean that you cannot learn moves for weapons you don't have, you just can't use those moves until you get a weapon of that level. So if you learn a Lv.6 attack but don't have a Lv.6 weapon, you cannot use that move until you buy a Lv.6 weapon. Also, each weapon you buy adds the designated Ego to your character.
Items are even simpler. They add however much Adrenaline to your character as they say. Some items, such as the Dropship and Tracker do more than just add to your Adrenaline. They have other important uses.