What size tires can I fit on my f150?

Hey guys.. so I have an 07 f150 supercrew and it's all stock. I wanna do some changes to calm my urges to buy a new chevy. I've always wanted some rims and big beefy tires, but I have honestly no idea how big I can go without rubbing the tires. I also don't have much interest in any sort of lift kit. I wouldn't mind some wheel spacers I guess, I've heard good and bad things about them so shoot me some advice!

So what are my options here? I'm kind of hoping to get a 20 inch rim, I have 17 inch stock rims and they're just too small and it looks awkward. But I don't know anything anyway so shoot me some sizes and (cheaper) brands of rims that are trustworthy! Not looking to spend a ton, I would say I would be okay with spending about $1800ish. Thanks