The pains of levelling up

Personally I find it quite difficult to collect epic anything in this game. I wish I could sell all my grey(common), green(uncommon) and blue(rare) to get purple(epic) power cells and such. At lv32. Epic options should be much more common or available in order to proceed in the game further. Also there is nowhere near enough sugar received in the game. Training requires quite a bit of sugar. Let alone 100,000 plus sugar for one level upgrade of a weapon. Justly so I think selling items would be great and being able to choose the perk you are selling for.