First let me say congratulations on that, it's good to see someone comfortable enough with themselves to actually be who they want to be. :D
You could always get a few dresses if you like those, maybe one or two just casual dresses you could wear out just for every day type situations, and one nice formal dress for events where you might need to dress up a little.
You can also just wear womens pants and jeans too though for when you don't feel like wearing a skirt or dress, most girls I know don't stick to just skirts all of the time and a nice fitting pair of pretty jeans is something I just have to have.
Also, some jewelry if you like it. It doesn't have to be fancy or expensive, I get most of mine at places like Claire's and at thrift stores. Just a few necklaces and bracelets.. and maybe a few rings to mix and match with your outifts, especially the casual ones, to dress them up a little.
I hope I helped you, even if it's only a little bit, and good luck!
As Jena suggested, try Michaels craft store for the transfers. While you're there, look for the Jerzees tee shirt display. They often have them on sale - 2 for $5.
Otherwise check the sunday papers for sales. Maybe your local Big Lots, Family Dollar, or other stores like that may have tees even cheaper.
You can also buy the blank transfer sheets at Office Max or Office Depot. Some discount stores also have them near the computer paper. Design something on your computer, print it on the sheet, then iron it on. The instructions are on the package.