Best way of getting RP

Use tournament sites and win it !

Real Money
Using apps = money x ad
or in some random draw haha

The best Way to XP is Ranking Games

Buy it with psc or so.
Just do it on the legal path.

try survey sites like prizerebel and inboxdollars got punch of gaming cards from them

Get a good job
and earn a money

Buying is a good way tho

You can get free rp on Tournament.

events league of legends.

Wait until some Riot Events starts!

Well..I don't know for any methods besides ur wallet :D