Hello. I'm an old contributor to DragonVale Wiki, and while not particularly active I stop by every once in a while.
Typically I am trying to survive the madness of Limited dragons. After a long period of inactivity on DragonVale, my quest to catch up is doomed - yet I shall still try. Somewhere along the way, I will resume breeding Steel Dragons in preparation for Metal and ColdShrines.
I feel it was unwise for me to choose Cactus Dragons to upgrade my shrines. Originally when I planned out which Dragons to use, I chose dragons to lower the breeding times. However, unless you have all the Treats (or DragonCash to buy those treats) that you need when you start, the time spent breeding will be near insignificant when compared to the time spent waiting for more money.
So my word of advice (yes, finally something that might be worth reading)...
When choosing which dragons to raise for upgrading shrines, use dragons which have a decent profit rate and can inhabit a Habitat that can hold a fair amount of coins. That way, the dragons being raised for shrines will actually contribute to your income.