This is the best attempt at Affinity that I could possibly build on the cheapest, yet reasonable budget. It uses a Frogmite build, but I would also suggest replacing Frogmite with Myr Enforcer. Etched Champion is the most expensive card in this deck. (Currently priced at $3.00 on SCG)
The style of playing this deck is very straightforward. Drop 75% of you hand turn 1, pump with Ghostfire Blade and Cranial plating on turn 2 (if you have a Springleaf Drum turn 1) and win turn 3. If you can't hit them hard enough turn 3, Shrapnel Blast and Galvanic Blast are great finishers.
I've considered several options for the construction of this deck. Etched Champion is a great win condition, but a great alternative would be Master of Etherium. He works like Signal Pest and gets gigantic when he enters the battlefield! Shrapnel Blast is a great finishing burn spell, but I've considered dropping it for Ensoul Artifact. I know it's not the fastest way to win, but I love the idea of a 5/5 bruiser on turn 2 and it's a great budget replacement for Arcbound Ravenger.
If you already have these when that you aren't using in standard, I suggest replacing any missing Blinkmoth Nexus you have with Tomb of the Spirit Dragon. It's great when you go against Storm decks or Boss Sleigh decks.
Currently playtesting and rebuilding as I go. Suggestions would be greatly appreciated and accepted!