Suggestions appreciated

I am on a budget. Anything above 7-8USD per card is pushing it.

I'm crap with sideboards, so I could use some help.

Card Breakdown

Creatures

Myr Retriever -- Returns almost any of my car to my hand

Steel Overseer -- Buffs all of my creatures to an absurd level

Vault Skirge -- Early-game pressure with flying and lifelink

Etched Champion -- I almost always have at least 3 artifacts on the board, so he can get past a lot of removal.

Ornithopter -- Flying chump blocker for free + metalcraft

Memnite -- See above

Equipment

Cranial Plating -- A win-condition, is very powerful in this deck

Enchantments

Tempered Steel -- Buffs every one of my creatures, a key card

Instants

Path to Exile -- Best removal in Modern

Double Cleave -- A good game-ending mechanism.

Dispatch -- A Path to Exile with no drawback (most of the time)

Other

Inkmoth Nexus -- Alternate win con

Darksteel Citadel -- land that gives me metalcraft

City of Brass -- Lets me trigger Cranial Plating's equip ability as an instant.

Thanks for any input!