Joggers are really good too, even less restrictive than trackies

I just wore shorts for my first couple of weeks but now have a pair of joggers. T-shirt is fine, though nothing too baggy as you don't want it to catch on anything.
Pair of grippy shoes is a very good idea. Some people recommend actually doing some barefoot training too, it helps you to learn proper landing technique; if you land wrong even on little jumps in bare feet, you will soon feel it! You really want to learn to land and roll properly ASAP to stop yourself developing any joint problems later