I am developing a game where you fly on hang glider. To add some realistic effect I want to add some clouds thath player can fly through them. I can’t use particles becasuse game is for oculus so every fps count;) Is there any posibility to made some clouds material that look quite nice and realistic?

If you want fly trough clouds you need volumetric system meaning that particles are only viewable solution. TrueSky has that out of the box, i havent tested it myself but aparently their rendering cost is not large. I am asuming that sky itself will be largest rendering part of your game so you have a lot room to go with good looking cloud solution.

i tried truesky and it works great.
the end result is obviously not 100% realistic but close enough for most cases.
there is a demo so check it out.