That effect for 4 mana is absolutely bonkers. You can basically always draw your entire deck if you untap with this/have enough mana. It's basically a permanent Mind's Desire.
By far the main thing holding this back is going to be the colored requirements. It's easier to generate 3 mana of the same color than 3 specific and distinct colors with things like black lotus.
You probably can't play this in a control deck since you can't really use this incrementally and you'll have a hard time closing games in one turn.
So, you are left with a combo deck. You need a shell that can play lots of spells to make sure you make the most of this card and an on the spot way to win. So Mentor, Tinker, Storm kill and/or Time vault.
I just don't see the Doomsday/Ritual deck that can support this and Gush being restricted means no Gush storm either.
So, you are probably looking a lot like an Outcome deck at this point. Are you playing this over Outcome or are you playing both? and if both, what are you cutting for this?
Unless you can somehow put together a Baral shell around this with manamorphose? How good would this card have to be to make a deck like that competitive?