5 point in purple make her steal purple.
Steal purple is useful against black widow (all versions), venom, c. Mag, moonstone.
I don't really see the point of 5 in black, 4 is enough for the synergy with hero strike tile.
Is lvl5 doubling the strike tile dmg as well? I doubt it will.
As for blue, lvl5 only leads to a half heal with count down tile on board.
It's useful in Pve, not very useful in PvP due to count down characters not being popular.
Anyway, not a big deal on how to lvlup, only thing that is a must is lvl4 black.