Just wondering if you should just stick with a certain Character until you get extremely good at it than you can experiment with other Characters or should you learn to play a couple few & switch it up?
It doesn't hurt to learn other champions but sticking to one as a main is also a good idea just don't learn champs in ranked
You can't be guaranteed your one champion in every game, so having backup options if your main is banned or the rest of your team has taken everything but duo bot is a good idea.
I do think sticking to mainly 1 champion is the best way to get better at this game over time because every time you play that champion, you can focus on watching and learning about everything else going on in the game that isn't your personal champion mechanics. Your map awareness and game sense take a huge hit when you have to spend so much time just thinking about how to get your champions kit to work.
If you want to climb the ranked ladder try to just play one champ. Then in normals learn others.
Have a few champs for every lane that you can reliably fall back on. This is the way I do it:
Top - 
Mid - 
Jungle - 
Support - 
ADC - 
I know these champs really well and I dont mind playing ANY of these champs. If you notice I have a different type of champs for every lane. now the first champ in ever lane is the ones I would say I main in that role. The others are just backups if they get baned. counterpicked or need a different type of champ to fit the team comp. Keep playing the game and find your own list.
I was maining one champ for a long while to just get good with her and know everything. I then started playing other champs to learn different rolls. It is a good idea to learn other champs in other rolls just incase the one you wanted was taking or (as someone previously said) the champ is banned.
