Hum... You have tutoring effects, so I'd play a toolbox deck of sorts as this color combination is tipically for mid-range decks. I'd keep Unstoppable Ash to the sideboard, I don't like it's ability all that much without
trample anyway, I'd play Indomitable Ancients over it anyday, and I WOULDN'T play Indomitable Ancients. You need a more consistent mana base, or to play Fertile Ground, I'm not sure which yet. For now, I'd add in a 24th land, probably Caves of Koilos. I'd also dumb down on fixlands a bit, maybe cut 1 Twilight Mire for another Caves of Koilos, and a Wooded Bastion for a Fetid Heath. Now you have a bit more access to black AND white. I'd pack in maindeck Thoughtseize, and I'd only play 3 Garruks. I'd probably eschew "free spells" and drop some Leaf-Crowned Elders for a third Colossus and 2-3 Profane Commands. I'd probably switch Rootgrapple for 2 copies of Terror and consider losing Nameless Inversion altogether for another Terror and the 24th land. I'd also consider moving Timber Protector to the sideboard, and only 1 copy, and maindeck Hypnotic Specter and 1 Oblivion Ring.
For sideboard, I'd lose Dolmen Gate (who blocks in constructed anyway?) and I'd consider switching Raking Canopy for Cloudthresher, although that may not be necessary. I'd ALSO consider (but that would depend on playtesting) Gaddock Teeg for the sideboard, and if there's enough space, maindecking some Llanowar Elves to increase slightly the odds of a turn-two Doran or Hypnotic Specter. And yeah, drop the Ancients!
