Riku Time

Hello. I couldn't help but notice that you've made a R/U/G deck. I enjoy the colour combination, so I couldn't help but look at what you've made.
From what I can see, you're trying to make a R/U/G aggro deck. If you are actually trying to do that, I would add Fires of Yavimaya and Deadeye Navigator. If you read Riku's ability closely, it doesn't say cast, it's only when a creature enters under your control. For four mana, you can literally double any creatures you have. Also, it appears that you're literally just trying to combine Gruul, Izzet, and Simic, instead of using the cards in a tri-colour blend. Might I suggest dropping some burn spells and adding more mana ramp cards like gilded lotus? Vexing Shusher is also a good choice.
Voidslime is way better than Cancel, I also like a majority of the shock lands that have been printed recently. Scry lands are also ok, but a bit slower. Perhaps you'd also like to drop a few more creatures and add in more spells that just do stupid big things? Unless you're trying to run more creatures, which is fine. ( I personally think that's what R/U/G is supposed to do, but that's just me)
I'd also look into Oracle of Mul Daya and Melek Izzet Paragon. Both would make your top deck a weapon.
Anyway, that's just my opinion. If you'd like, you're more than welcome to take a look at my Intet the Dreamer deck. It's slightly different, but I think the main concept is still there.
www.mtgvault.com/ifonly/decks/sweatpants