Curious what peoples plans are for advancing, My strategy of only doing every 5th or so Nymph seems to work decently well up to 500. Concentrating on:
Frea
Tiger
Penguin
Monkey
Dragonfly
Dragon
Flowergirl.

(all of which have 4 second lvl 10 skills... start is a bit rough until I get Penguin maxed) Things dramatically slow at 500 though. I expect I'll need to start using shards to upgrade a lot, and possibly reduce the interval between Nymphs.

Incidentally, I have to strongly agree with what somebody else said, Fantasy shards seem to be exceedingly rare.

I have gotten:
10 fire
8 Water
7 Earth
9 Electric
10 Light
8 Dark
1 Fantasy

My "gut" feeling is that they simply don't drop from shardkeepers. You only get them from rebirth and/or wheel. (I *think* I got mine from rebirth) Seeing as the vast majority of my shards come from shardkeeper kills, that puts 'em at a severe disadvantage.