Originally Posted by
roguebee
All the advice above is good. The only additional comment I would add, is when you level up, just feed them enough to get to level 3. Then wait until you are ready to evolve them to finish feeding through level 3. Coins are the same whether the color bar is blank or full, but you defer the expense of feeding.
The opinion I would offer is to consider the evolution time as a decision on whether to sell from the nest or keep to evolve for gems. I sell off those 20+ hour fails (Island and Magic come to mind) rather than tie up the evolution temple that long for a small gem.