How many champions should I main for my main lane?

in Bronze = 1 In Silver = 2 In Gold = 3

Honestly, I would just say 1. But if you really want to play more champs limit it greatly. You can probably climb further taking 1 all the way to Gold instead of trying 2 in Silver. But it seems fair enough.

At least 5 if you're really going to main, plus you need two main roles so at least have 3-5 for the secondary.

all of them

Main 1

Have 2-3 back up picks youre also good at for each role

depends on who you're playing.

if you're on a popular champ that gets picked/banned a lot u need another to use in case.

i would say "learn" (play them enough to get to mastery lvl 5ish or so) enough to outstand the ban phase and being last pick and having every other one of those champs get picked.

or i just recommend at least 5-6 non-mains per role.

for example, i usually main garen (dont play him as much nowadays since im super bored of this game and just do stupid builds, but hey, when a friend wants me to not be stupid, i wont), and he has been someone I can usually win most matchups with in my experience. after that, for me, the line goes tryndamere, darius, renekton, sion, olaf, kled, trundle. i do play jarvan but i hate him toplane since his sustain is garbage, so he's kept to jungler status for me.

3

Two. Maybe three if your first too are really popular and not always available. Not more.