Becoming a Super Saiyin in Dragon Ball Xenoverse is something every Saiyin will want to do. It is a skill you do not automatically learn while playing the game so some people might miss it.
Yep, go for the "I want more usable characters" wish instead, You get Gogeta SSJ4 the first time, Super 17 the second time and Omega Shenron the third time.
When you collect the Dragon Balls
Don't make the wish "I want to get stronger" it's useless.
Now someone should write a separate article about the mind-blowing way that you can unlock Super Saiyan 2 by buying it from the store using zeni.