I will like to know wich champion that i should buy ( wich one is the best), riven vs darius or fiora , i know that fiora got patch but she still look good but i am not a expert player so i will need your help for that pick pls????
Get Fiora. Go full AD Runes. Start Dorans Blade. Rush IE and max W first. GG
or Get Darius to go Dunk Squad.
No Riven
Out of the 3, I would say Fiora for the most well-rounded champion.
Riven requires a lot of practice to get the mechanics down for the fast Q plus AA combo and the third-Q wall jump. She has unparalleled trading power due to her high AD scaling, but it also limits her to build only AD to maximize her potential. She also had her hp/5 reduced significantly, meaning that even if she win trades at first, she will lose in the long run due to no health regeneration. Back in S3, a fix to that was to buy a fortitude exlixer and force fights earlier on so the enemy can't regenerate their health, but that is no longer possible in the new season. She is still a good pick; however, due to her lack of regeneration, she has no chance in certain matchups.
Darius is arguably the best champion for against melee. His bleed DoTs makes him a lane bully early on and often zone out enemies at level 2. The downside is that Darius has no gap closers and struggles against Ranged champions. As well, he offers no use other than damage in a team fight. The new item, Righteous Glory somewhat fixes his lack of mobility, but he is still a very risky pick considering that Ryze is free this week.
Fiora's passive allows her to trade with her opponents often with no consequence. The constant regeneration lets her stay in lane longer and soak up more exp and gold. Her Q and W can be used to dodge attacks. She has a passive AD steroid, a short AS steroid, and a mobility boost on top of her two leaps. As well, her parry allows her to block AAs ever so often. Although her ultimate has been nerfed recently, it is still quite good. As always, it provides free damage and life steal against her opponent. The only downside is that she doesn't have high natural mitigation, so don't rush into a team fight first.
My minds telling me Fiora but my hearts telling me Riven 
Darius. Fiora is getting a rework sometime near future and Riven is played a lot.
