Riven is an amazing melee damage dealer. She's able to put out quite a bit of damage and being badass at the same time. Her attacks are aoe based and have a huge impact in a team fight if done right.

Pros:
-Great harasser
-High burst
-All attacks except auto attacks are in the range of a small aoe.
-Good escaper



Cons:
-Picked on by range/cc
-Distance closers are a bit limited.

Greater Mark of Desolation Greater Mark of Desolation x 9
Greater Seal of Resilience x 9
Greater Glyph of Warding x 9


Greater Quintessence of Desolation Greater Quintessence of Desolation x 3
You can swap the quintessences for flat hp, or movement speed.

CORE ITEMS

OR

Start off with a doran's blade and focus on last hitting. Once you get your stun, you can q-combo your way into the enemy and stun for a nice harass. On your first trip back, if you're being harassed a lot and haven't farmed well, just grab boots and some pots, if you have enough money buy Ionian boots for the very much needed CDR. Afterwards grab a brutalizer for even more CDR, which accompanied by some arp and damage is a very nice early item for Riven.

By Midgame you should be working on your bloodthirster, you will notice a huge increase in your damage output when you get it. If you properly time in auto attacks in between your abilities, you will be shredding your enemies apart. A standard, E-W-Q-Q-Q combo deals some very nice harass. If you're too far from the enemy after using E, weave your way with Q, and stun when in range.

Lategame, you should have youmuus, sunfire cape,frozen mallet. Riven is a "get in your face" type of champion, so you need survivability to stay in the mess of the team fight. Your abilities do enough damage, so items like infinity edge aren't necessary. Rush into team fights after your tank initiates and deal a ton of damage to everyone. You won't die easily.


Personally I like to grab frozen mallet because it'll add more to your AD, along with a nice slow. But if the other team is pounding you with AP, obviously grab some MR like force of nature or banshees.
Other items to consider:

and
With this build you should have more than enough movement speed, so flash is much more useful for escaping and ganking. Flash, E, and Q will allow you to reach opponents very far away as well as escape (make sure to keep clicking to tell riven where to go in between your E and Q's.

Exhaust allows those pesky runners to be killed with much more ease. You'll notice as riven after your standard harass combo, your enemy will be running a lot, exhaust secures a lot of kills for you as riven.

Max out Broken Wings first, followed by Ki Burst, then valor. This allows for the most burst possible early game. Level up your ult at 6, 11, and 16.

Runic Blade (Passive): Riven's abilities charge her blade, causing her to do bonus damage on her next autoattack. Riven can store up to 3 charges, but only expends one at a time.
Nice boost to your auto attacks, however this can be used inefficiently if you Q Spam, weave in your auto attacks in between your q combo.

Broken Wings: Riven steps forward and lashes out in a series of powerful sword slashes. This ability can be activated up to 3 times in a short period.
1st Use/2nd Use: Deals damage to a small area in front of her
3rd Use: Jumps into the air and slams downward, causing a larger impact nova that deals damage and knocks nearby enemies back.
Your main source of damage and harass. The ability that defines Riven, similar to Karthus's Q, Riven will jump out and deal damage based on where your cursor is. Deals a lot of damage for harass with a knockup on the third.

Ki Burst: Riven damages and stuns nearby enemies.
Very nice ability to stun everything in a small area around riven. This is part of why your burst combo works so well. Although it's only a .5 second stun, it's enough to get in extra damage and that knockup.

Valor: Riven dashes forward and gains a shield for a short duration.
Pretty much the ability you use first, close the distance, gain a shield, overall nice ability.

Blade of the Exile (Ultimate): Riven's sword reforms, giving her a percentage multiplier on her total attack damage, extended range on her damaging abilities and basic attacks and the ability to use Wind Slash once.
Wind Slash: While Blade of the Exile is active, Riven can reactivate the ability to emit a large shockwave that deals damage to all units hit based on their missing life.
Your ultimate. Makes your broken badass sword more badass by making it longer, giving you more range on your attacks and more damage. So you gain more damage, range, and a one time ability that deals more damage based on the hp of your enemies. Overall, huge damage buff.

Once you start getting into team fights. Your combo will look something similar to: Activate ult-->Valor-->Ki Burst-->Q combo, and Wind slash when necessary.

There are a lot of ways you can use your abilities to dodge skill shots and to escape. Valor being your best ability, it gives you a shield and makes you dash in a direction, giving you leeway in the case that you do get hit, your shield will take part of the damage.

Farming early game isn't bad for riven, your Q can really rake in some money. Mid game with Ki Burst and Broken wings, you decimate waves and riven becomes an amazing farmer.

Riven is an extremely fun new character that isn't too hard to learn. But the ability to use your auto attacks with your passive is what separates good rivens from the bad. This build is by no means perfect, I am open to other opinions and criticism :D.