SSJ2 - It should be obtained at a few levels above half of that (65) and it results when you obtained SSJ through Shenron.
Second and Third Grade Super Sayian. it should be obtained as a certain type of skill sayians can obtain (from getting ALOT of exp)
SSJ3 - It should be obtained at the almost end of the game. SSJ3 gives away life energy. which is only burned when in this transformation. once it goes out you have a 50 percent chance of going to the other world (also a map idea) or just dying and respawning.