With $300, you could build UGr Scapeshift (No Misty Rainforest), which is a very powerful deck and surprisingly difficult to hate out. Going by TCG mid, here are the expensive cards:
The rest of the deck can be obtained very cheaply, and you can save even more if you already have shocklands and/or snapcasters for standard.
Feel free to PM me for a list.
What might be more reasonable though, is to have some Prophetic Prism to get you the white mana, but at that point, you're probably just better with UB.
Another good idea is to buy/preorder 4x Common/Uncommon sets from RTR block and Theros, as they are around $25 per set and ensure that you don't have to spend an unreasonable time hunting around for good uncommons like many people in my area did while looking for Experiment One/Burning-Tree Emissary/Flinthoof Boar/Ghor-Clan Rampager.
This is absolutely my favorite deck to play, I successfully played it after the Stoneforge/Jace bannings, and right after M14's return of Doom Blade, and I think with the loss of Snapcaster Mage and the reprinting of Thoughtseize, we can form a very similar shell to what was good right after the stoneforge ban, that had Inquisition of Kozilek and Jace's Ingenuity, as well as CREEPING TAR PIT.
For an unknown meta and with 197 cards unknown at the time of posting, this is the deck skeleton I will begin working with and tweaking as we discover the rest of the set.
Your best bet is probably the Talismans of Dominance and Progress. Unfortunately, you will take some damage from them, but these are the cheapest ways of getting that extra U a turn early. Extraplanar Lens could also be good, just remember to cast the talisman on turn three or the lens on turn four so you have another two mana up for a counterspell.
Remand is very good in scapeshift and a necessity in MonoU Tron, the latter of which has become incredibly popular lately due to it being a very cheap deck that preforms very well. As it was not reprinted in Modern Masters, the supply is much lower than some other staple uncommons like Kitchen Finks (a $8-10 card before MM), while the demand is continuing to increase.
Just tested at FNM, Syncopate is awesome. Replaces Essence Scatter, or maybe 2-2-2 with the three counterspells. Aetherling with 1 mana up is easy, just respond to the exile with a second removal spell. Of course, more open mana makes it harder, but by then it is late enough in the game that you should be able to stall with a removal spell each turn.
Who says permission is dead? Sure, a resolved Thragtusk is a pain in the ass, and a Cavern'edAetherling is "impossible to deal with" (it's actually pretty simple), but we have our own ways of being a pain in the ass.
This deck is particularly effective against midrange decks, while faster decks such as Naya Blitz and Junk Aristocrats are more of a challenge. As a control deck, this is the grindiest, so anything with Sphinx's Revelation is a piece of cake.
Permission style control has been off the radar since Avacyn Restored, but I really think Doom Blade is the last card needed to make this deck work for anyone itching to play a game of magic entirely on their opponent's turn.
4 Rakdos Cackler
4 Firedrinker Satyr
4 Burning-Tree Emissary
4 Ash Zealot
4 Gore-House Chainwalker
4 Minotaur Skullcleaver
2 Pyrewild Shaman
4 Magma Jet
4 Lightning Strike
Total ~ $280.
The rest of the deck can be obtained very cheaply, and you can save even more if you already have shocklands and/or snapcasters for standard.
Feel free to PM me for a list.
4 Watery Grave
4 Nimbus Maze - UB member of speculated cycle
4 Dimir Guildgate
4 Mutavault
6 Island
4 Swamp
2 Aetherling
Draw: 7
4 Inspiration
3 Opportunity
Counters: 8
4 Syncopate
4 Psychic Strike
4 Doom Blade
4 Far / Away
3 Devour Flesh
Misc: 6
4 Thoughtseize
2 Cyclonic Rift
For an unknown meta and with 197 cards unknown at the time of posting, this is the deck skeleton I will begin working with and tweaking as we discover the rest of the set.
On to the decklist:
4 Watery Grave
4 Drowned Catacomb
10 Island
4 Swamp
4 Nephalia Drownyard
Creatures - 2
2 Aetherling
4 Snapcaster Mage
4 Tragic Slip
4 Doom Blade
4 Far / Away
3 Devour Flesh
Counter - 6
4 Essence Scatter
2 Dissipate
Draw - 7
4 Think Twice
3 Forbidden Alchemy
3 Crypt Incursion
3 Pithing Needle
3 Dispel
3 Illness in the Ranks
2 Curse of Death's Hold
1 Psychic Spiral
This deck is particularly effective against midrange decks, while faster decks such as Naya Blitz and Junk Aristocrats are more of a challenge. As a control deck, this is the grindiest, so anything with Sphinx's Revelation is a piece of cake.
Permission style control has been off the radar since Avacyn Restored, but I really think Doom Blade is the last card needed to make this deck work for anyone itching to play a game of magic entirely on their opponent's turn.