Hello and welcome. What country are you in? Cage choice is one of the first things. While cleaning up your room you can work out where a cage could go
It can be quite creative rearranging things. Something like a 90cm Ikea Lack coffee table or a chest of drawers, can be a good place for a cage. You won't want a cage smaller than 80cm for a Syrian or 70cm for a dwarf hamster.
Plus all Cypher's advice above!