I need 4 new summer tires (been putting it off due to the expense, if you're wondering why I'm doing this half way through June

)
I have rims and need tires to fit them, or.... ?
the tire size for the rims I have are P195/50R16
Crappy tire doesn't have any in stock, but can order, though pricey.
Should I a) downgrade to a P195/55R15 (same as winter tires/rims) so that I don't have to pay so bloody much for the tires or b) look around for cheaper tires and just get them put on at Crappy Tire (only because it's convenient and relatively cheap)
One reason I'm stuck on Crappy Tire is that I have nearly $300 in gift cards that I can put towards the purchase, but at the prices I was quoted, that'll only buy 1-1/2 tires

Suggestions of places to buy tires? And maybe how/where to sell rims if I downgrade?
Thanks!