Board Thread:Questions and Answers/@comment-24392826-20140107140622/@comment-7743566-20140108003748

for the process you described the 8-15 linked page uses the gold dragon example, which from your question it seems you have already read. and yes you are correct using cards that are max leveled as feeders does give a better (Card Experience raising) boost to the card that it is being fed to, but it is NOT worth your dorri or the feeder cards to level of a feeder card before feeding it to the card you are really trying to level/evolve.

Depending on the rarity of the card you are really trying to level (and your access to abundant dorri) it may make sense to farm FP from Major churches in the Envisioned Realm feature and in turn exchange them in the 10000 FP Free card pack as the common and uncommon cards in there are drawn already at max level enhancement.

In MY OPINION if dorri is not an issue, i'd be fine using these feeder for level cards up to Super Rare rarity, (but not the final form version, which counts as Mega rare), because the dorri cost for enhancement scales with the evolution and rarity of the card you are enhancing.