First clean your room. Any furniture you can move easily, push to the side. Put everything that needs to be put away in a pile on the floor and start with the biggest stuff. Keep grabbing stuff working your way down to the little things. When there is nothing left, vacuum.
Move the furniture around so you have a bedroom area and a study area. Make it so there is enough space to put a wall with a doorway up. Get plastic storage bins with drawers and put them near your desk. Fill up desk drawers and these drawers with:
Paper, pencils, pens, crayons, markers, colored pencils, erasers, tape, scissors, glue (etc.)
If you are a crafty person like me I have plastic bins for my craft stuff too.
Get a comfy chair and put a radio near you desk and invest in some soothing, calming music. On your desk get really tiny desktop plastic drawers, file sorters, your computer, a phone, pencil cup, sticky notes, a memo pad, and behind your desk put a bulletin board.
Good Luck cleaning!