As you play and level up, simply do NOT spend any skills at all, until you're at level 30. Once you reach level 30, you'll have more than enough points to max out two trees. Each of the three trees has one skill which requires level 30, so do be sure to wait until you're at least that high a level.
So, once you are high enough level, simply save the game, max out a tree (or two), wait for the corresponding trophy to pop, then reload the save and repeat for the rest.