In theory, I save up my gold for the more expensive EI/CI's that I'm after.

But in reality, I end up spending about half of what I have on me during events for the reduced-price event commons. It's about the only time I buy commons these days, except for the rare occasion I can justify the gold expense for some item that would 'make' an avatar combo I've thought up.

It IS hard to save up what I need, with my spending habits. >.>'
That's why I try to shunt 500g over to my mule whenever I can, during those times I'm not saving up for an event or something.

So, I guess I spend it on Event commons, and then occasionally on CI's that I've missed.