Learning how to better use your powers, for example.
A fire user could make the particles to move faster, generating more heat, or if we don’t want to enter physics department, we could just he’s concentrating more energy in one point making the fire hotter (changing the flame color and so), concentrating a big fireball in a really small fireball and letting it explode at once, to generate a big boom.
Water user, could get better at making things colder, or making the water jet faster, or more pressurized to make more dmg
Earth users, same idea, but it would be a defense oriented concentration, but he could make a really hard bat, or a cage.
Wind users, make it faster, so fast that one vacuum blade would appear, then faster, and 2 would appear, and so on
Shadow user name would be eviroment dependent to make more dmg, but he would get a almost infite potential in dark place, he could move faster, create wall, cages, weapons, everything from shadows, but in light place he would get less shadows and less powerful.
Light users, same as shadow, but instead of getting solid objects like weapons from the power, they would get explosive powers similar to fire users, more light, more power. (Shadow would be more melee focused and light more ranged focused).
Psych would get dmg proportional to the will stats (20+will) or something like that.
I really can’t think about time powers.
All the power could be unlocked with train, for example, we can’t say a wind user who didn’t got the fly power, at the start, would never learn how to fly by himself, right?
Everything would be the same as technology, but instead of using parts, it would be something else, like use more time, a mechanic would need only parts and 1 slot of free time. A power user would need 2 slots of free time to unlock a new Power. (It could also be training materials and 1 slot of free time)
That is my ideia, you can use some parts of it, or none of it, only suggestions :).
Ps: ranged attacks (like rays) would all get the marksman bonus, same with melee.