Expansions?

Hello all,

I am very confused about what expansions I should buy on Steam. I would like to own all of the Civ5 content.

I currently own,
1. Brave New World
2. Gods & Kings
3. Ghengis Khan's Mongolia

What other packs should I buy? Is it cost effective to buy the Gold Edition even though I already have Gods & Kings?

I'd get the $10 gold upgrade. Buying the DLC a la carte will cost you at least twice that.

The gold expansion costs $40 on Steam. Can I get it cheaper somewhere else?

Why not get the upgrade?

Thank you. I did not see the upgrade edition.