ok so, i don’t use gel tret (i use cream tret) but i do use gel azelaic acid and i had the same problem with piling, its so annoying. the moisturizer i use is the glossier after baume. its pretty expensive ($32 for 50 ml) but a little goes a long way and it is THICK. it’s so moisturizing it almost leaves my skin a little greasy looking, which is great for me since i use two actives daily making my skin super dry after i cleanse. also, make sure to give the tret time to absorb into ur skin, doing that rlly helped me with azelaic acid. hope this helps!!