There is really only one rule involving use of your items.
DO NOT, I repeat, DO NOT use any of your weapons, armor, or ANYTHING that aids you in battle in a topic unless it has been approved (unless it's an existing shop item), bought, the gold has been transferred, and you have added the item in its template to your Inventory in the "Inventory" category.
All you do is create a topic called "(Insert name of your character)'s Inventory" and add items to it directly from the shoppe as you get them bought or approved.