Riven is melee champion but instead of building her as a normal attack damage champion ,focusing attack speed and damage , I build only damage since Riven has altogether 7 skills u can use making it almost unneeded to use normal attacks.

I start with critical chance rune marks , attack speed seals ( for faster creep grind early ), and more critical damage as glyphs . The explanation is simple . But I'll talk about it in the items build chapter.

I start with 21/1/8 masteries focusing damage since it's most important for this champion.

As you can see i start with Long Sword + Health potion .Reason for that is that all skills get bonus damage from the base damage of the normal attacks you have . After that i get boots of speed because even tough you may have 4 dashes you really don't want to waste those getting to your target rather than smashing his head.After that i focus on getting Tiamat since it gives you bonus damage and hp regeneration and most importantly SPLASH damage , after that the sequence follows : Trinity Force - because of the Sheen ability and the splash taking into consideration you got 7 skills to activate you can devastate almost all enemies in 3 skills early and in 4-5 skills late game, next comes Bloodthirster it's simple why you need that : to boost your skills damage even more and get you lifesteal so you don't need to go back to base so frequently , next in line is Infinity Edge the reason for that is bonus damage and critical strike chance combining it with the runes and the Trinity Force critical strike chance you are almost unbeatable 1vs1 at this point and last depending on enemy team you get another Bloodthirster if they are squishy if they got tanks you may want to get a Black Cleaver and if they focus you alot better get Guardian Angel .

At this point you have all probably guessed where I'm going with this sort of build .
You must always remember that because of the movement speed and the 4 dash skills + Flash summoner skill you are BOUND to over commit in chasing or diving on turret but keep a close eye on your allies and enemies .

So you must always start using Broken Wings ( Q ), after using it u hit the closest target with a normal attack since you got plenty of damage thanks to the Trinity Force after that to avoid getting damage if the enemies are more than one use Ki Burst ( W ) followed by a normal strike at the same target at this point if you haven't focused the tank enemy should be half health , now use the Broken Wings next followed by normal hit as normal ( always remember Trinity Force is you main source of damage at least until you make Bloodthirster so USE IT ) then you probably want to get some shield on yourself to decrease the damage you take so use Valor ( E ) but not the way so you get away from your enemy but so you get ahead of him/her now you can hit 1 more time and it's most certain the enemy is dead by now ( if not tank of corse ). You probably have noticed I don't have you using your ultimate it's simple that's a last resort skill use it if there are more than one enemies you have to face so that it increase your range of attacks also increasing the range at which you can Use the effect of Tiamat splash damage , which is crucial in a team fight after that you want to use your Ultimate second ability at as many enemies as possible who are still standing that is or if you chase since it's got some pretty nice range .
Most of you have probably guessed it without me saying it that all of your playing style should circle around the Trinity Force both mid game and late game.
What i forgot to explain is the Tiamat it's basically like this you do tons of damage so why limit yourself to one target when you can trash everything around you so it's a very good item for early mid and late game allowing you to farm early game , giving your team advantage in team fights mid and late game and after combining if with trinity force you can most likely take on 2 opponents and not worry about what I'm going to do once i kill one of them and all skills are on cooldown it turns out that the other opponent is low hp and running or low hp and overcommiting most of the time if you have saved your ignite or ultimate until then it's highly likely you'll live it trough.

The best thing is you can almost always run away from enemies using Valor + Broken Wings and if they close in on you use your Ki Strike to increase the distance .

Contra : what i see mostly as a mistake done while playing Riven is the fact that most people assume that since you can close in on a target you are initiator ... THAT IS NOT SO ... unless u want to do a tanky build which isn't alot of fun to play . So i see people charging into ganks just because they move fast and fail really hard mid and late game .

The main idea while playing Riven ATLEAST for me is the bet behind wait for an opportunity and when you have one smash their bones . The damage output is really incredible but early and mid game you are almost as squishy as Shaco so charging in isn't always the best idea . I

What i do is wait for teammate to get into a fight and then attack enemies usually it leads to either them trying to run away or you kill someone mostly having your teammate at half hp or above which is good .

Another good thing for Riven is the Harassment you can really get on the nerves of almost anyone IF YOU GET MOVEMENT SPEED else it's no harassment it's just charging which you want to avoid early game since you are SQUISHY !

OK that's the main thing i can say about this champion so early after it's release hope you find it useful if not well maybe you can make a build that I can learn from . Please rate and comment on this build .

PS : so far 9 games using Riven 8 wins 1 loss using this build so it's not impenetrable and flawless but it's good my scores vary from 21/10/X (overcommitment) to 8/2/X(they surrendered)
In the lost game i had the score 11/9/X those guys were pretty good and we weren't :D