Once you begin to find a rhythm with the cards, youll intuitively know when to stop, when to cut the deck, and when to begin drawing cards
Overly situational and not wildly effective
With a bit of the top of my cube shaved off, I went over my creature curve to confirm that my cube has sufficient small creatures for Ribbons of Night to usually have a target, enough fixing that it can be splashed, and insufficient card advantage that Ribbons of Night becomes attractive to folks wanting it
A 3/1 for 2 with some upside is usually playable
This allowed Soldevi Sage to shine, since it had ample time to dig through your library for your best cards/answers to your opponent's problems
Play cards off the top when theyre useful or when you need to find better ones, or leave them on top when the cost is too high or you dont mind holding them for later