I dunno man. I just thought that every level was a Orange gift potential.
LOL
I was wrong.
Now I realized that to play smart, you invest skill in level you see there's great potential. If the level is throwing at you too many Blue tiles, too many mobs hitting you hard, or tempting 4 - 5 Red tiles combos (Attack x2) -> you just move on and finish it quick.
But getting Cakes from "EPIC" or "Legendary", Purple keys criticals is still dumb imo.
I'm farming non stop level 6.3 right now. I use Acid Traps from mob to reduce Blue Tiles and increase chances on building great stacks YELLOW/PURPLE.
Thanks for the hints guys.