you can main whatever you want , but id say at least have 5 champions you would want to be good at , one for each role ,
ADC
SUPPORT
JUNGLE
MID
TOP
me personally , i like to have at least 10 champions that i am comfortable with playing , .. 2 for each role , just in case of counter picks , or just something that would help out team fights in general ... basically , whats best for winning either my lane or team fights in the mid to late game .. but .. always let it be something that you are comfortable with playing , dont play certain champions just because they are considered op or has the highest win rate,..
Save up for lvl 3 runes , lvl 1-2 runes arent worth it at all
Get to lvl 30 , play a few normal matches to get used to playing against other players , i wouldnt exactly go right into ranked , until you have somewhat a good feel for your roles that you want to main / play ... and the champions you would want to main / casually play
and also no , you dont need a team to climb in ranked , having a team that you know and trust can make it easier to climb ,but the wait time to start a game might be a bit long because most likely it will be placing your team against other teams who also know each other
You can play ranked solo as well , but will be placed with random people , climbing can be a bit harder this way , but its not all that bad
but uh .. yeah
[slayer-pantheon-thumbs]