I'd lower it before rims, but it's up to you. No one really notices a lowered Camry since it isn't all that low, so you won't look like a fool riding stock rims on a lowered car. But if you get some rims without lowering you'll probably get the SUV look.
I would drop it first. Most of the kits to drop it only drop like like 1.2-2.2 inches (I think). Most rims that are not like 20" should fit it with no prob. Plus, if in the end you don't have enough money to buy new rims, you would still have better handling over the stock.