You can only transform during a fight, you will not be transformed until you do, whatever your PL(You must transform during fight to use ability and cannot jump from ssj1 to ssj3 must go change one level at a time).

Saiy-Jin:
SSJ1: PL 1,500(+1 to all dice roll)
SSJ2: PL 3,000(+2 to all dice roll)
SSJ3: PL 5,500(+3 to all dice roll)
SSJ4: PL 7,500(+4 to all dice roll)
Golden Oozaru: PL 9,500(+5 to all dice roll)
Mystic: PL 15,000(+6 to all dice roll)

Human:
MegaHuman1: PL 1,500 (+1 to all dice roll)
MegaHuman2: PL 3,000(+2 to all dice roll)
MegaHuman3: PL 5,500(+3 to all dice roll)
MegaHuman4: PL 7,500(+4 to all dice roll)
UltraMegaHuman: PL 9,500 (+5 to all dice roll)
MysticHuman: PL 15,000(+6 to all dice roll)

Android:
ProtoTypeA: PL 1,500 (+1 to all dice roll)
MegaForm1: PL 3,000(+2 to all dice roll)
MegaForm2: PL 5,500(+3 to all dice roll)
MegaForm3: PL 7,500(+4 to all dice roll)
ImperfectForm: PL 9,500(+5 to all dice roll)
PerfectForm: PL 15,000(+6 to all dice roll)

Changling:
KiHiddenForm: PL 1,500 (+1 to all dice roll)
Change1: PL 3,000(+2 to all dice roll)
Change2: PL 5,500(+3 to all dice roll)
Change3: PL 7,500(+4 to all dice roll)
ImperfectForm: PL 9,500(+5 to all dice roll)
PerfectForm: PL 15,000(+6 to all dice roll)

Namekian:
InhancedNamek: PL 1,500 (+1 to all dice roll)
Super Namek1: PL 3,000(+2 to all dice roll)
Super Namek2: PL 5,500(+3 to all dice roll)
Super Namek3: PL 7,500(+4 to all dice roll)
Elite Namek: PL 9,500 (+5 to all dice roll)
Mystic Namek: PL 15,000(+6 to all dice roll)