Should I buy Riven

Personally i have riven and is hard to use, darius is not that hard, and is a good duelist, but the most of times is banned.

If you have good reflexes go riven. If you want to have fun go darius.

Get fiora, she's stronger than both of them and a lot of fun

She's great. But be warned you'll be despised on the forums, focused in every teamfight even when it makes no sense, and ridiculed for in any game you do poorly.

Based upon the fact that the reason you give is "I have saw many people be op with .", I say No for two reasons.

1. The people you watch "be OP" are people who are very good with Riven, who are showing you exceptional examples.
2. You will be spending all your IP on a champion you don't even know if you like at all.

If you buy her and really want to do those "OP" things with her, then be ready to dedicate a LOT of time into learning and practicing with her.

But in my biased opinion, as a Riven main, she's completely worth picking up!

shes one of those champions that you have to stay with. darius is easier to pick up. riven is hard to play effectively.

go with darius. hes really fun and easy

If you have the time and effort to put into it, pick Riven. However, prepare for literally everyone you play with or against assume you will rage/feed.

No don't really

No. She is one of the hardest champions in the game, and is currently not that good right now unless you put an absurd amount of dedication and practice in.

I'm gonna agree she is very hard to play and can be extremely frustrating. Fiora can be fun but she's hard to master also, squishy front lines take practice on engaging.