If we're not talking about really fine finishing work in this room, I'd think a miter saw on a stand and a circular saw would be the main tools to use. The circular saw for breaking down plywood panels for shelving, etc. and the miter saw for cutting the framing (2x4/2x6 etc.)- a circular saw with a speed square would probably work for the framing as well if you don't really plan to do a lot more construction after this project? For the panels, use some clamps and a long straight edge (straight piece of wood?) as a guide and you're probably set to go. You already have a drill, as others said, plenty of power with an extra battery if it's cordless makes sense as well.
Of course, if this project is a good "excuse" to start purchasing a lot of tools, then there are probably thousands of dollars in tools you would have to have.
