This is VERY LONG, so feel free to read or skip, up to you! :)
While i may only be Gold 3 ATM, at one point i was 1 game off of plat, but ended up getting an AFK due to a power outage so RIP that idea. Back in season 5, i ended up being placed in bronze 4, but climed my way all the way up to silver 5, then was silver 1 in season 6, gold 5 in season 7 and climbing this season; so i at least have some experience with getting out of elos and ranks. I will try and give you tips for each lane, but i am a ADC/Jg player mostly with a little bit of mid, so i will have more tips for those lanes than others. Ill also give you a few tips of champs if you've listed them and i play them.
The champs you listed, some of them i would avoid playing.
For top i would avoid playing Riven. I still have yet to see a good riven in gold or lower, and it's rare to see them be any good until diamond. Tips for top, I'm not a top main, but i would just try and play something tanky and not feed. Farm under tower if you have to and look for TP ganks around the map.
For Jungle i would Avoid playing Lee Sin. While he's an okay jungle, he can and WILL fall off and be useless late game. With him not having green smite or sightstone, it's hard to get reliable wards for ward hops. Unless you can land 90%+ of you're Qs, he has no good way in, and you HAVE to be able to Insec 100% of the time or there's little point in playing him. If you're jungle then here's tips that i do all the time. You NEED to get the Scuddle crabs. They give 100+ gold and a shit ton of XP, Usually people will go for the top side 1st, so if you think you can fight them, you can try and go for top side sudds. If you are a very shitty early game jungle, DO NOT risk it, go for bot side after your buff. Make sure you give your team the kills. While you may not have as much fun, it's how you will climb. If you're team is fed then they can carry you, if you have all the kills then they can focus you and you die then you have a bunch of under fed teamates that won't do anything. If you can, focus on ganking bot.** ADCs are THE STRONGEST CARRIES IN THE GAME**do not ignore that lane. If the other ADC gets ahead, you will have a hell of a hard time winning, while if you can get YOUR ADC fed, they can carry a game.
I play Kha'Zix as well, so if you're playing him focus on trying to get a strong early game lead. Unless the other team's jungle is a strong dueler(
as an example) keep strong vision up and some good map awarness, but feel free to try and be in the other team's jungle, both counter jungling and killing the other team's jungle. Back if if there's a MIA lane though, you have you're jump for a reason. As an early game kha if you KNOW you're limits and know how to teamfight almost perfectly, feel free to take the early game kills. That is something i do and it will work most of the time. It's a high risk(as if you fuck up or don't know how to play when ahead, you WILL lose the whole game for you're team) but a VERY high reward(I'm talking like 1 shotting 2 squishys in the back line and winning the game for your team). Unless you understand the other team, what the game is looking like and you're limits, just give kills to your teamates.
For Mid i would be worried about Zed, but he's not that hard. As long as you understand the big parts of his kit he can be played at lower ranks and do fine(He's one of my mains). For my mid lane tips, roam. Roaming is a huge part of mid, shove the minion wave and try and come gank a pushed up bot lane or top, try and be a mini-jungle. Even if you're match up is bad, then roam and you can get fed.
Zed is one of my best mid laners so here's some tips i got for him. Keep track of his shadows, you can juke like a fucking MAD MAN if you can keep track of shadows. If you're facing someone like an Oriana or Lux, you know then when you come out of your ult, a CC spell will be coming right at you. Before you ult onto someone, trow out a Shadow with you're W and hop back the SECOND you get out of your ult. People will almost never expect it and as long as you can use you're Abilitie's off your shadow, you can get some fucking sexy kills. Mind you it will be hard to 100--0 people with out the standard tripple Q combo, so poke them low before trying to engage. If you can mange minion waves well, try and hit 6 before the other mid laner, the second you hit 6 before, engage IMMEDIATELY. It catches SO MANY PEOPLE off guard.
For ADC i think Lucian/Xayah are 2 champs that are extremely strong and easy to play while still having room to improve. For my tips i would say focus more on last hitting than being agro, A kill gives you 300 gold, but if you are up about 15 or so farm, you are on par with the other ADC on gold if not a little bit ahead. Only engage and poke if you are built to do that. Cait/Ez should be poking 24/7 and draven should be punishing the other ADC for misstepping every chance he can get(with with over extending himself that is). Wait for your support to engage before trying to go in, or counter engage if you can.
I play BOTH Lucian and Xayah so... Wall of Text(TM)
Lucian is prob one of the strongest dueling ADCs in the game(behind a good vayne) his burst is fucking off the charts and can delete ADCs like an assassin if he get on them. Make SURE you do not waste you're passive, weave auto attacks in between you're spells. Start every combo with a E if you can as you're passive will lower the cool down of your E. You're BEST burst combo if you can is E-AA-W-AA-E-AA-Q-AA-E-AA, and that will usesually fucking melt any squishy. You can cancel the W animation with your E, So if you're trying to kite, you can W behind and E forward almost at the same time(it's kinda hard to do but once you get it, it will be easy) so you can get the movement speed for kiting. another strong engage tool is your W-E-AA and just keep going with the standard burst combo. You're Ult can 100-0 any squishy and half health any tank if you can last most of if not all of the shots late game, try and use W before your ult though for movement speed. In lane try and keep a minion between you and the other ADC, whenever they stop to auto a minion, Q that said minion and hit the other ADC off of you're Q. Try and play lucian with an agro support as you will have strong lane pressure that way.
Xayah is really strong as she can make her own CC, use Q-AA and you can get almost an instant root off, it can catch people off guard at level 2. Use you're Ult to avoid any kind of CC or burst spells coming after you(this CAN avoid a zed ult being put on you, kinda like fizz E). her self peel is fucking INSANE. i will sometimes not even get a defensive item because of this. a 100% crit chance xayah is fucking INSANE. Poke with her feather splash damage(kinda like lucian) and if you can, fight in the jungle, a Runnan's Xayah fighting in the jungle i would say is tied for the best DPS you can get(with jinx fishbones in jungle).
For support you can mostly play anyone and do fine. Just focus on trying to baby sit you're ADC, if this means you only counter engage, do it. I went for bronze 5 all the way up to silver 5 by being a 1 trick Braum player and only counter engaging. for tips i would just say make sure to get a ton of wards and don't play too over agro, you will die.
Just pick 2 roles to main, have 3-4 champs you can play in those rolls, and be able to play at least 1 pref 2 champs in every other lane. I hope this helps, and good luck on the rift man, hope to see ya in the upper ranks one day! [slayer-jinx-catface]
and allmost 
and i start farming killing botlane and jax camp bot so i buy 4 wards to ward all his jungle (i allways do that after lvl 5 i know he will came ) jax was going fed on top on akali vs vayne (i really dont know why people play adc against some good ap or something but akali was on 10 min 1/10 ) and mid also feed i have in 20 min about 22 kills and 4 times died i had allmost a full bulid but jax was having full bulid allready if he kills me we lost.. so tell me what you can do when your team feed so much but this is fkk every game every fk game.. i decide to find some good player to play with me but you can win 2v5 a mean if you are really insane player like someone who played more then 2000h hahah.. anyway i win that fight you know how ? i ask them do you wanna win they said yes then follow me and do what i said.. then akali said i will not you stupid polish and i answer him/her akali i am not polish i am from germany i dont wanna get fight with you just wanna win the game and she say no you will not win this she/he go died and write on /allchat go baron they are on botlane all we was and i say to my team they will no go baron.. anyway she go afk and somehow we kill them i dont know jax was farming on top we kill entire his team and win that was mistake from him.. i was having luck that game beacuse 3 players was bad but they want a win they didnt troll like akali they just dont know how to counter his enemy.. somehow i started play Azir and i lose 4 games from 5 i didnt feed they feed and surrender i told them dont we have late game but i am one they are four you now what did happend. thank you guys all for this.. i will try harder to place my rank in high i get in silver 2 for promo silver 1 only play botlane and its for me good luck everyone [sg-lux]