From a fellow samurai, not sure of the exact % increase per installment of store tp, but as a low lv sam i was getting 9-11 tp per hit, and now after lv 30 I average 11-13 tp per hit.
Tp store increase with more very 10 lvl or 15 lvl gain.. i cant really remember clearly. but i think its at lvl 15,30,45. and with meditate Sam is the key person in SC.