Just do some poking around, look at pictures, find out what you want to work up to. Asking for the "best" combos with morphs will only get you responses of "Whatever you like best." Pastels are especially variable and used in a TON of different combos, so just find something you like. The picture forum here on BP.net is awesome, but there's also that world of ball pythons morph gallery, NERD, and almost all breeders online have a collection gallery where you can see all sorts of snakes.

There's no real straightforward answer to what you're asking. There's not really "harder" morphs, just things like recessive genes that take a little longer if you don't have a visual. Stick with the Dominant/codom morphs and you should be good