Using your own item
If you are using a item in a role-play and you consider it yours. Then it either must be bought or created.
Using a surrounding item
If you wish to use a surrounding items, that doesn't belong to you. Then you can.
For example, you can grab a crate and throw it on your opponent, as long as you don't carry it around on other role-plays and don't say that it's yours.
Created item using
Before using a item, that you have created. You must have it approved.
Bought item using
Before using a item, that you have bought. The bought item must be putted in your inventory. This will be usually done by the sellers.
Limited Items
Limited items means that you can use it only once, and after you have used it, you must buy a new one.