So first off I want to make it clear that you can main whom ever the fuck you want, I mean I play Aatrox regularly ffs and do quite well for myself considering how weak he is! lol So no matter what anyone says learn and practice the champs you really enjoy and add on to that list later :)
Anyway, I'll separate my answers based on position to make it more readable lol
Top: For this position you basically will want to have a couple tanks and a couple carries, so as to fit into any team comp you can and to avoid being countered or countering yourself because your champ pool is too narrow.
So
and
for your carries aren't bad, Fiora is hella strong but you will often find her banned, while Jayce on the other hand is on the weaker side with fewer good match ups, but he still does have them and his own effective playstyle, so just make sure you have backup carries, like
for example. As for tank options
is always a fantasic one, post-rework ofc, but you will need another. The thing is after her nerfs she is very weak to champ with either true damage or who can bully you early game since your trading potential was just gutted. So like say the enemy team picks a Darius and your team NEEDS a tank, you don't really want to play Poppy into it, so maybe have a back pocket
or
to fall back on to avoid hard lane counters.
Mid: For this one you should have at least two AP champs, maybe even three, before you really start to main an AD mid.
and the others are generally very strong, so if you really enjoy Zed and can play him effectively then certainly continue playing him, but you don't really want to pigeon hole your team into a full AD comp just cause you can only play Zed mid and your AP choice would be countered or something.
is a good all around option, but he is also very counterable, so have someone else who can do well against typical TF counters, like maybe pick up
or
as back ups, or both! lol
Jungle: This one is similar to top, you want a couple carry options but also a couple tank options. Say you're last pick and your top laner has locked in Fiora and your support is Sona or something, you will have to fill that tank role effectively or your team could suffer if it doesn't snowball, which is not something you should rely on.
and
are both very strong early game junglers, but they kind of do the same thing, so maybe for carries focus on an early game one, like Lee Sin, and one more for late game like
so you don't fall off, just incase you need late game power in your team. Then you really only need like one tank champ to fall back on really,
,
,
, and others like them are super easy to play and to learn and perform the tank role quite well.
ADC:
and
are good choices, both strong right now, but I'd suggest three. Basically if you only have 2 to play here and one of them gets banned and the other team locks in a counter to your other choice then you're straight up fucked. ADC is my worst role so I couldn't really say who to pick up, but the gist is to have 3 ADCs you can effectively play.
Support:
and
alone basically cover all the ground you need, Sona is ok as well and has her place, but if you can grab her or Janna right now you might as well always grab Janna lol I'd recommend adding
to this list for the sole reason that he's a very strong support and works very well with most ADCs.
Hope this helps at all! I made sure to use the face icons for the champs I think you should focus on to start, so it's easier to remember them should you come back to recall something :)