The choice of doing either most of the training by yourself, or by joining a party (esp. party quest) will prefers different order of skill point build, however, the end result should be the same, and I wouldn't go into the detail of how each skill affects your ability. Since the SP distribution is essentially the same as what everybody will do including normal thief, such information should be found in the main article for Assassin.

Solo-oriented build

Level 30: +1 Claw Mastery (15%)
Level 31: +2 Claw Mastery (20%) +1 Critical Throw
Level 32: +2 Claw Mastery (25%) +1 Endure
Level 33: +2 Claw Mastery (30%) +1 Endure
Level 34: +2 Claw Mastery (35%) +1 Endure
Level 35: +2 Claw Mastery (40%) +1 Drain (102% 16%)
Level 36: +3 Claw Mastery (45%)
Level 37: +3 Claw Mastery (55%)
Level 38: +2 Claw Mastery (60%) +1 Drain (104% 17%)
Level 39-42: +3 Drain per level
Level 43: +1 Drain (130% 30%) +2 Haste
Level 44: +3 Haste
Level 45: +3 Haste
Level 46: +2 Haste (+20 100sec) +1 Critical Throw
Level 47-55: +3 Critical Throw per level
Level 56: +1 Critical Throw (maxed) +2 Claw Booster
Level 57: +3 Claw Booster
Level 58: +2 Claw Booster +1 Haste
Level 59-61: +3 Haste per level (maxed)
Level 62-66: +3 Drain per level (maxed)
Level 67-69: +3 Claw Booster per level
Level 70: +1 Claw Mastery (maxed) +2 Claw Booster (180 seconds)
Party-oriented build