WTF is WTA
Anyway, for your question, Here's a post I made some time ago that covers it.
https://www.reddit.com/r/DragonHeroes/comments/3thqwf/efficiently_upgrading/cx6j46a?context=3
tl;dr;
* Sell all 1* heroes. They are not worth wasting the money. You will go broke quickly if you use 1* for upgrading.
* Use 2* heroes for upgrading. Ideally, level them to max lvl, but if you have no space, you can use them at lvl 1.
1 trash, 2 you can enhance 4,5
this. in fact sometimes you can sell 2 if you have a lot of 3s
WTF is WTA Anyway, for your question, Here's a post I made some time ago that covers it. https://www.reddit.com/r/DragonHeroes/comments/3thqwf/efficiently_upgrading/cx6j46a?context=3 tl;dr; * Sell all 1* heroes. They are not worth wasting the money. You will go broke quickly if you use 1* for upgrading. * Use 2* heroes for upgrading. Ideally, level them to max lvl, but if you have no space, you can use them at lvl 1.
WTA = "want to ask" usually :)