21 lands are way to much. I also played a budget-affinity-build pretty similiar to yours and removed land after land (at the end I played 17). You should add a playset Spire of industry, remove 7-8 basics and add cheap artifact cards like Welding Jar and Arcbound Worker.
Steel Overseer is way to slow for your Deck and pretty useless without Arcbound Ravager.
This is old list:
Steel Overseer is way to slow for your Deck and pretty useless without Arcbound Ravager.
This is old list:
4x Cranial Plating
4x Darksteel Citadel
2x Etched Champion
4x Galvanic Blast
1x Glint-Nest Crane
4x Island
3x Master of Etherium
3x Memnite
6x Mountain
2x Myr Enforcer
4x Ornithopter
4x Signal Pest
4x Spire of Industry
4x Springleaf Drum
4x Vault Skirge
1x Welding Jar
2x Whipflare