For anyone who's cheap or on a budget, try Craigslist.
I haven't bought a set of tires (except trailer tires) from a store or online in the better part of 10 years. Takeoffs for popular vehicles, especially trucks are plentiful and cheap. And if you search hard, you can find premium tires that someone bought then typically decided weren't big enough and is selling at a serious discount. When you're talking some of these pickup tires that are $400 a pop, $800 - 1000 for a set is a screaming deal.
Last set I bought was a complete set of takeoff 20" Ram 3500 tires and wheels, brand new, $1000. Came out to $800 out of pocket after selling the ratted out old tires and pitted rims.
Previous set of like new Toyo MTs, $900. Set before that, new BFG ATKO, $200 a tire.
I've gotten 2 sets of tires for the wife's car in the last 5 years. Both half price of new.
Trailer tires I only buy new though and last few years etrailer.com has had the best prices and selection for light trailer tires.