Market Stall: With this effect it would be more of a permanent than a spell. U C, spells are one-time things. The effect could be a bit too strong, as it generally lockdowns the opponent and can cause hand congestion especially with you reversing his creatures and chaining Stalls, so he'd be eventually forced to discard, but... with a 2 turn effect it'd be alright, I geuss.
Newt-On Charger: Could be cheaper for that ability. See Gnome Gemfinder for cost tips. Also, who's Issac Newton?
Time Chamber: Such a low reward of 2 Time quanta doesn't justify creature sacrifice. The damage a creature would deal is worth more than 2 Time quanta.
Wormhole: Generally, the creatures of yours are better than the enemy's, but you could combine this with waiting
for Godot until the enemy starts his strategy while you don't play anything and then casting this. Notveryuseful. Also, you can't mix cardcostcolors in this game. Flocking MtGians.
Erosion: And if the enemy doesn't have Earth creatures, what am I meant to do with this card? Get it in rear? (
http://tinyurl.com/yzl2kko) Kill my own Shriekers in Earth/Time? You haven't thought much about this card. Also, remember this one small rule: Cards that can only target 1-2 elements aren't good, as the enemy may not have them.