Max slots/skills are unavailable until the level cap is raised. There'll be 10 Soul Boost trees total, so we have quite a few more left to go.
The current limits at 1.5k level cap are:
Equipment Slots: 2
Blast/Strike Arts: Level 5 (starting at Lv1, +1 per SB tree)
Special/Extra/Ultimate: Level 2 (starting at Lv1, +1 at 3rd SB tree)
Presumely, the level cap will be raised the game develops. Eventually we will have 3 eq slots, Level 10 Blast/Strike arts, and Level 5 Special/Extra Ultimate arts.
