Yup, if have to choose due to limited budget, I'd also prioritize tires first. In my case, my tires cost more than my rims even though I'm very happy as well with my rims (but they're used ones)!I disagree.
Original RPF1 with ling long tires? You'll end up in a ditch.
That's the reason also why I only upgrade to 17' not 18', coz 18' tires that I will go for will be even more costly.