1 RP per win
I honestly think this is a great idea but I might possibly get flamed for posting this for whatever reason. But my suggestion to you Riot directly is that you incorporate 1 RP per game won. Yes I know you need to make money in order to keep jobs and support your employees but this is not such a bad idea and let me tell you why with three pros:
1: Average skin cost 975 RP. It would take an average player around 2000 games or so win or lose half his games. 2: Many players often fall short of being able to buy a skin they really want and it forces them to buy another 10 or 25 dollar riot card. Keep in consideration a lot of players are young teens that most likely don't have jobs or live with their parents. 3: Many players will be motivated to play well in games if they are dedicated enough to try and win more RP. This could potentially improve player skill and also keep players from intentionally playing poorly after losing their lane or poor performance from their team mates.
All in all there's a lot of pros to this idea. I'm not all so sure of the impact it would have on you riot specifically but hey its worth a shot to try and implement this. YOLO SWAG PEACE.