Riven is one of those champions that I used to play a lot of purely because the challenge was fun to me and nothing else. I suppose it depends what your intent with the game is, and if you seek to reach high ranks via the ladder or if you just plan to casually play Normals. In my case, I used to play her primarily in Normals, and such never affected me except for the occasional teammate that may have gotten a little too upset at my performance [sg-lulu]
If you seek to play her at a genuinely competitive level, I do advise you to watch a lot of videos on her; There are tons out there, and they can definitely help to expose you to some combos that you might not have known existed beforehand. Since a lot of players like to main her (I presume you know the stereotype about Riven Mains..) there is plenty of content out there to help you learn about many things her kit involves, and thus you can hop into a practice tool or Normals match to try them out.
I'm in no way trying to discourage you, but personally I find sticking to a champion for a really long time is difficult to do as I often get sick of the abilities in due time no matter how much I liked them in the first place. Riven, for me, is one of these champions where after some time I just got bored with her kit. I do hope this doesn't happen to you, but be weary that not all mains last forever, and so increasing your champion pool (If you're trying to play competitively) is going to make your experience last longer, in my opinion.
Best of luck ! [sg-kiko]