Hey,
First of all, welcome on the forum!
Do you play 1 VS 1 or multiplayer?
In both case, you should work on your mana base. You should get rid of all the lands that come into play tapped like the Vivid, or
Evolving Wilds... And replaced them with better ones. I know it can be expensive but it's always useful and you can sell them later if you need some cash back.
There are some cards I would remove like :Glaring SpotlightJourneyer's Kite (mana rock instead,
Thran Dynamo for example)
Gem of Becoming (mana rock instead)
Mogg ManiacDarknessPhyrexian Obliterator ( BBBB is hard to get in a tricolor deck)
And some mill cards, if you want to play mill, you should dedicate your entire deck to it, so I would also remove:Ashiok, Nightmare WeaverRiddlekeeperI also see you play around dragons (maybe not enough), there are some good tribal cards like:Patriarch's BiddingDragon TempestCrux of FateAlso
Cyclonic Rift is a must have...
You may want to get a lower curve (especially if you play 1 vs 1), you can find other discard cards and add
Waste Not.
Ways to remove the graveyard of your opponent :
Bojuka Bog,
Nihil Spellbomb ?
Finally, don't hesitate to look to my decks, especially if you play multi