You'll need a total of 79 skill points to level up all of your abilities. You start off with two free skills - Silent Strike and Concentration.
50 of those skill points will come by levelling up all the way.
16 are rewarded through the main story quests.
3 are rewarded for some of the side quests - Acquired Taste, Redmaw and Queen's Gambit
5 are up for grabs for getting at least half suns across all 5 hunting grounds
4 are received by completing 4 of the 5 cauldrons (PSI is part of the storyline, not a separate encounter)
5 are received by completing all 5 Tallneck encounters.
I got 7 skill points after collecting the last vantage point. For me it was the last collectable in the game, so I can't be sure if it was for just the vantage points or completing all the sets.
You shouldn't have too much trouble grabbing this Trophy by level 50. If you go out of your way, you can get it earlier than that.