Hello, My name is Sleepy :)
I've main Riven for a year now and it helped me climb low elo, From Bronze III to Gold I.
Riven is difficult to play for newbies but if you played her for like 10-20 games you will start learning the mechanics of her kit.

RUNES FOR RIVEN ARE:

x9 MARKS OF ATTACK DAMAGE - Standard marks for damage.

x9 SEAL OF ARMOR - Mostly all the top laners are AD so you'll need this.

x9 GLYPHS OF CDR - The main goal for Riven is to reach 45% cdr.

x3 AD QUINTS - Obivously Riven is an AD Fighter/Assassin so AD QUINTS will help her to deal more damage.

Riven Skill Sequence : R - E - W - Q

R = Blade of Exile - Max it whenever its available, Rivens broken blade turns into a whole large blade, it gives her a bonus 20% attack damage and Wind Slash that makes Riven throw a 3 lines of Wind-ish aura.

E = Valor - if you'd think this is the companion(bird or eagle or something) of quinn, NO. This skill makes Riven to dash in every direction your cursor is aiming to and it gives Riven a shield.

W = Ki burst - its dragonball Z ? NO. It makes Riven raise her blade fast and stuns the enemy around her.

Q = Broken wings - this skill makes Riven slash in a direction, plus you can use it 3 times, the 3rd time you use it, it makes Riven jump in a splash area.

Passive (Runic Blade) : Riven charges her blade and it produces damage.

SPELLS : TELEPORT AND FLASH

TELEPORT - used in many different ways like split-pushing, joining team-fights, defending towers, and baiting.

FLASH - most important spell in the world, it teleport's you from a short distance.

NEVER EVER-EVER USE RIVEN IN RANKED IF YOU'RE NOT FAMILIAR WITH HER KIT AND HER USES.

To Get good in Riven, U wanna autolock her in every single normal game. just joking with ya.
THE ONLY WAY TO GET GOOD ON RIVEN IS TO PLAY, PLAY, PLAY, PLAY, PLAY, AND FINALLY, PLAY.

The Combo for riven is random, any way you want to use her just don't die.

I usually go for this combo's : (AA - Auto-attack) (F - Flash)
R - AA - Q - AA - Q - AA - W - AA - Wind Slash - Tiamat - Q
Q - AA - Q - AA - W - R - E - Q - Wind slash
Q - Q - R - Wind Slash - F - Q - W
E - Tiamat - W - AA - Q - AA - Q - R - E - Wind Slash

So that's it
IF you want to improve PLAY, PLAY, AND PLAY.
Always be positive and don't let anyone block your way to success.
Don't rage at teammates if they're bad or feeding 'cause raging is one of the reasons you're not at the top.
The only solution to feeders is carrying them and proving that you are good at League.