Riven is a champion that is best played as tanky dps. She does very well early game with lots of harass from skills and a decent shield. She also has good mid game and late game capabilities.

I play riven quite aggressively, by ganking a lot and harrassing at level 2 with her q and w. Although riven can easily be shut down by silences and CC. Silences is her worst fear, you will be in the middle of using your q and BOOM silence and you will end up standing there with nothing to do.

My playing style allows you to get firstblood or lane dominance in solo lanes. You must play aggressive with riven early game. Im not saying dive their enemy teams turret at level 1, just harrass them with q auto attack q auto attack q auto attack. This should bring their health bar down by half maybe more.

My build is very good IMO, it works for me and i average 10-15 kills a game in 3v3, more in 5v5. My deaths also range from 0-5 usually 2 deaths.

THIS IS MY FIRST GUIDE! HOPE IT HELPS YOU PLAY RIVEN TO HER FULL POTENTIAL!

Pros
-High mobility
-Shield that scales on AD
-AOE Stun
-Manaless (spam your abilities =D)
-INSANE EARLY GAME DAMAGE
-ULT is OP
Cons
-Shut down hard by CC
-Need to time abilities right
-Cooldown dependent
-Squishy early game

For Marks i choose 6 Great marks of desolation and 3 Marks of strength. For Seals i use 9 Greater seals of resilience. For Glyphs i use Greater Glyphs of Focus. Finally for Quintessences i use 1 Greater quintessence of Strength and 2 Greater Quintessence of Desolation.

The extra AD in the beginning is needed since at level 1 you only have boots and wont do much damage unless you get a dorans blade. The Armor pen is for her abilities and attacks since they are all AD. The Armor and MR is for survivability early game so you can harrass and not get punished as bad.

By end Game you should have Ionian boots of lucidity, Youmuu's Ghostblade, Black Cleaver, Frozen Mallet, Blood Thirster, and Wits End.