My THIRD try at making this deck. The first involved no rares, which was cheap but not necessarily effective. The second actually got somewhere, but then someone at work mentioned another win condition, and I flipped my table and decided that this is Simic: adapt, evolve, graft. Just keep trying until you get it right.
This new deck has not one but two extra ways of winning. One is to become unassailable: Herald of Secret Streams is the biggie, but Zegana, Utopian Speaker and Skatewing Spy also do some good work. The second is to Golden Snitch it: build up, drop Simic Ascendancy, throw down Galloping Lizrog and/or Biogenic Upgrade to cause a huge spike in +1/+1 counters, and just be on top of things. The whole rest of the deck focuses around building to the point that these bombs have the desired effect... and, if not, on just going so tall and wide that the opponent can't handle it.
My criteria for this deck are simple: No card worth more than $1. (I also have an internal challenge to have as many cheap rares as possible, as I think it would kind of be funny to have a deck filled with a bunch of cheap "expensive" cards.)
Changes to this deck have primarily involved smoothing out the early game. It's wildly mana-hungry and also not properly balanced: I can't count the number of times I've had to mulligan with 5+ lands or spells, and a couple of times that I played it against my wife (running Forest Clobber -- Treefolk Tribal Ramp), I would end up with spells all in one color and lands in the other. But when it works... Whoo boy.
If you can figure out something to replace Llanowar Reborn with, you can make this deck Pioneer-legal.