I'd question whether or not you really need 3x Crystals. I'm not much of a Wizard player, but if going with a Gate, I tend to go Gate + Harmonize (on the Gate) on turn 1, then get a creature out on round 2. This way, you don't lose so much momentum and have more mana to spend in the early game, although less in the late game. And notice that Harmonize on a Gate costs 1 mana less than a Crystal, and helps your Gate to activate earlier and more frequently, which is especially useful if otherwise your opponent might opt to go melee or equip a bow or even Medition Ring to reduce their spell casting.
You can also Harmonize a Wizard's Tower, if that's another early game plan for you. If you still plan on winning through mana economy, I could envision:
1 (20): [mwcard=MW1J07]Gate to Voltari[/mwcard], [mwcard=MW1E20]Harmonize[/mwcard] (Gate)
2 (12): [mwcard=MWSTX1CKJ02]Wizard's Tower[/mwcard], [mwcard=MW1E20]Harmonize[/mwcard] (Tower)
3 (11): Deploy a creature ([mwcard=DNC03]Devouring Jelly[/mwcard] or [mwcard=MWSTX1CKC08]Gargoyle Sentry[/mwcard]) and get to work! Or, if your opponent isn't applying any pressure and you really want Channeling 12 on top of your turbo Gate and Tower, you might drop 2x [mwcard=MW1J12]Mana Crystal[/mwcard]s.