Board Thread:Game Discussion/@comment-5996974-20130613122758/@comment-10687721-20130613130147

ah, I see, sorry. In that case, I wouldn't upgrade them. Use them to upgrade your top 9 because: 1) they'll probably never make your deck, and 2) upgraded cards don't seem to give directly proportioned experience when used as upgrade fodder themselves.

I usually sell all my R1 and R2's for credits and use R3 and unneeded R4's for upgrading fodder.