I'm pretty new to the league of legends scene (Relatively, at least. Ive only clocked a couple months :P) and have only played about 10 different champs. However upon playing Riven, i immediately not only found a champ whose play style i liked, but i also started to do significantly better. This is my first guide on Mobafire, and is not really meant for the entire world to see ;) i mean, feel free to use it, but i don't have a guarantee that this will help you see that Victory message at the end of every skirmish. The item's aren't going to work the same for every game, obviously, and you should probably build to defend against AP and AD accordingly, but this is a good base build (:

For Riven to be effective, armor penetration runes are a must. I've tried using a flat AD rune page with her, and while it tears apart the competition in bot games, using a mixed set of marks helps her cut right through enemy defense runes and masteries. Flat MR glyphs help Riven a lot, as she is very susceptible to the corresponding attacks, and flat armor seals just help her with early game sustainability. Throw in some strength quints to piggyback off of the armor penetration your marks do, and you should be good to go early game. Running Riven with this set of runes drastically increased my win rate with her, and i can almost guarantee that it will do the same for others.

There isn't much i can say about the masteries i chose for her. Riven is meant to be a bruiser, in my eyes, and that's how i play her. The masteries reflect that. I dont see what could go wrong if you put more points in defense than offense, but taking the points out of vampirism reduce Rivens infamous sustainability.