Soft hackles are easiest.
Pheasant tails are only slightly harder.
Hares ears are next.
Once you get the regular hare's ear down pat, try adding some weight.

Tie them all in different colors and you have a pretty good nymph selection.

Worry about princes and zug bugs next.

The beauty of soft hackles is that you can tie them with different body materials to mimic the nymph patterns you don't know how to tie yet. They won't be a perfect substitute, but they'll be pretty good.