You can wish for anything BUT:
1. A transformation level
2. Extra Powerlevel
3. Earth Balls Cannot kill anyone
4. No more thne 2 attacks per wish
IF you wish for this:
1. immortality: you cannot go above the 3rd transformation level of your species. example: saiyan, cannot go above ssj2, but you still gain power level
2. more attacks: you cannot get attacks that have power level requirments beyond your own!