Well I'm sure they have Swamps and Islands (The very best card in Magic). And who wouldn't have an assortment of common counter magic i.e. Counterpell, Mana Leak, Prohibit, Rewind, Exclude, etc...
Add a little cheap common removal like Terror, Diabolic Edict, Expunge, Dark Banishing, etc...
Put in just about any common creature with some kind of evasion such as Thalakos Scout (Shadow and an untargetting effect for 1 discard), Foul Imp (Flying), or Rishadan Airship (a 3/1 Flyer).
To spice it up add some more annoying commons: Recoil, Repulse, Rushing River, Boomerang, Duress, Mind Rot, PROBE (This card is Some Good).
Want lots of card advantage from common gems? Deep Analysis, Accumulated Knowledge, Brainstorm, Gush, Inspiration, etc...
Boring? Yes. But heck, it's Blue/Black! Don't think of it as boring, just shift your paradigm and think of it as; "How can I make my opponent any more annoyed than he/she is right now?"
My Motto:
"I don't play to Win, I play to Not To Lose."