Welcome to Riven101.
This is my first build, why i choose Riven was because she really caught my attention when she was released i basically like all melee champs like garen, irelia, and wukong but when riot released riven and watching how different her mechanics are to the others she really shined for me as a champ. ive played riven a couple of times and i am pretty impressed on how she plays as a champion. early game she can just go in to lane and just hit the enemy repeatedly and walk away pretty much unscathed, mid game around lvl 7 -10 she starts to become a different champ in her own with her ulti active you will have greater distance on your auto attack plus that second ability wind slash you can just stay in battle until you are near death.
So i hope this guide helps

Im only showing 2 spell because i think these are essential for riven
this will save your *** if you are overrun by enemy champs, just dont use it while traveling or you will be screwed
works well with broken wings and with ki burst because once exhaust is finished you can just stun you opponent and get an easy kill

this is a good passive skill because it stacks with your auto attacks and gives it a bit more damage
This is your main damage ability i max this second. you can use spam this once the cool-down is finished.
I max this ability first because putting it basically it will save your *** if you get ganked the stun helps!!!!
in my combo rotation i start with valor for the shield and then i go stun and broken wings
a good ulti provides extra range in your standard attack and has a nice secondary ability which can help with your damage output

greater mark of desolationgreater seal of resiliencegreater glyph of wardinggreater quintessence of vigor

reasons for these runes:
.Geared for early game power.
.able to survive all most any encounter in lane while dealing decent damage

Pros:
. good melee fighter
. good mobility
. combo champ
. early game very good harasser
. great at chasing champs

Cons
. no escape skills
. decent farmer

I really do hope this build helps people play riven better if not comment what is wrong with it i accept all comments to try and make this build a hell of a lot better like i said at the start this is my first build and i am willing to continually update this build until it is up to the standard as some of the best builds on this site.

Hope to see you on the fields of justice,
Zaxcorat