Sage mode must be obtained as a limited or taught by someone who knows it. Sage mode can be trained in rp with an admins permission.To increase power of you sage mode you must earn them with stat points. You gain points the same way as stat points through fighting and training.

The starting stats are for the following ranks for Sage Mode:
S-rank/Kage: 400
A-rank/Anbu: 300
B-rank/Jonin: 200
C-rank/Chunin: 100
D-rank/Genin: 50

Sage Mode
Strength: (how much strenght your sagemode gives you)
Speed:   (how much speed your  sage mode gives you)
Stamina: (how much stamina your sage mode gives you)
Agility: ( how much agility your sage mode gives you)
Endurance: ( how much endurance your sage mode gives you)
Chakra Reserves: (how much more chakra your sage mode gives you)
Senjutsu: (how much chakra you can asborb per post)
Duration(how long you can stay in sage mode.)

For every 10 points in duration means you can mantain the form for 2 post.