I really like that first ability. It's going to be a feel-bad moment if you don't have any other creatures, though, making me think this should have haste. It also seems like an uncommon more than a common.

The second ability on its own pushes it out of common nowadays - as opponents need to keep track of it, and your available mana, constantly.

I love the first ability though - and think it's fine, if green is dropping 5-mana creatures and doesn't have any other creatures; well, you're not doing it because you're on the offensive, are you?

I think that the regenerate is to good at for a common and should be or something.

You shouldn't get "Regenerate target creature" on a common at all. (Except as a oneoff sacrifice effect, perhaps.)

Mm. Not unless you planned to have a limited environment where people stared at each other for hours on end. I do think you can feature it... but only if the ability is impractical for regular use. I wouldn't start using "regenerate target creature" on common, unless it cost or more.