Hey just started playing 
and really love all the options you get in your combos and playstyle with her. Still i often enough lose lane (mostly to tanky champs) and I need to know what I can do to make my laning stronger. I usually catch up in the late game cuz.... damage is unreal on squishies :).
Trading in lane with riven requires proper management of her cooldowns. Early on it's especially important that you don't fight unless you have equal or more minions than your opponent as well. Riven is very squishy, but more important she also has very bad sustain, so you want to take as little damage as possible.
One of the best ways to trade in lane is to dash in with your shield for an auto. If they attack you back, your shield absorbs the damage and you can then use your W and Q to disengage. This puts a decent amount of damage on them while you take none in return, plus they may have wasted cooldowns and mana on your shield. Keep in mind that if you use all of your cooldowns for damage, you're going to be stuck in an auto war which you will probably lose early on against fighters and tanks (like Nasus, Shyvana, Irelia, Trundle, etc.). So always save at least 2 of your gap closers to run away in those matchups, and it's generally best to run after you stun with W.
A ton of learning Riven just comes from knowing your matchup and knowing what your opponent is capable of. You can only get that from experience.
Riven is one of the most match up intensive champions you can play, in my experience. The only thing you can really do to get better with her is to learn her animation cancels, and play those match ups until you're good at them.
She's hard to learn but really rewarding because she's so fun to play. I'd also advise against just picking her top lane if you don't know who the other team's top is, since she has a lot of counters.
If you hear anything, let me know. I don't main her, but I want to have her as a viable choice for toplane, and right now she isn't one for me.
Please don't ever let the thought of maining Riven cross your mind, once I had to play with a Riven support because a "Riven main I can carry" didn't get to go top. Can you guess which botlane lost?
Riven's playstyle is already toxic, especially with the mana regen nerfs, and we don't need any more "I got 24 kills last game as Riven" mains infecting league.
GG
Im not high ranked or anything but I will say that with Riven knowing your lane opponent is pretty important, more so than usual. Knowing when youre stronger than they are, and taking advantage of that point in time is hugely important as Riven because she pretty much needs kills to become relevant late game (or lots of farm).
Against someone like Nasus, youre best bet is going to be aggressive play early on when he's weak. Try to zone him away from farm and freeze the lane so he cant last hit, preventing him from building stacks. Obviously youll eventually need to leave and he'll get stacks but delaying his power for as long as possible is key.
Against someone like Renekton, you never really have an advantage. From level 1 onward youll lose trades and all-ins if the Renekton knows what theyre doing. In this situation you need to just try to soak up as much xp as possible and farm under tower while asking your jungle/mid for ganks.
The whole dynamic of top lane is really unknowable as far as who youll find up there now unfortunately. Just last game my Riven teammate was up against an Akali top (which id never seen before myself), so itll be hard to know what to do going into every matchup. At that point all you can do is give it your best and try to feel things out as the game progresses.
So long as you learn something from every game, youll do fine and improve. Keep a positive attitude and don't let any toxic players get you down. Riven is a fun champ and if you keep at it youll get good with her.
Thanks for the tips guys, guess ill just keep practicing. Just played a match against an ahri and got reckt :P Im pretty sure thats not supposed to happen.
