Need help improving my Riven early game

So I'm brand new to Riven, only having about 10 games on her and I've noticed that I tend to overestimate her power early game by a lot, in laning phase I almost always end up feeding thinking I can out damage the enemy. Late game I have no issues so I just have to figure out how to transition smoothly. Should I start Shield and a Pot and play super passively? Normally I start Long Sword 3 Pots but that doesn't seem to be enough. I know it depends on the match up too but after having played against two Teemos and having completely different results I need more advice. I do know how to fight in the minion wave (cc drops aggro) but I still feel like I'm getting out damaged.

How do I play it out? Are there any guides out there for this?

Thanks!