Started playing 2 months ago. Bought Lulu, Ahri, Riven, Jayce, and Kha'Zix, and Fizz on sale with RP. Also bought a week-long IP Boost during vacation break to fill out 2 full rune pages.
Spent $30 so far with 1729 RP still unused. And yes, I buy champions with RP. I don't give a nut about skins and I don't have time to farm IP either. Instead of spending 2-4 weeks farming, I spend 10 minutes working for the dollar bills for a champion.