- I personally advise knowing two roles and be sure to know support in case you get autofilled. More often than not you will get the support role.
- For your champion pool I would say about 2 per role. One thing to know is if you play the mainstream champions such as Yasuo or Lee Sin you will require more champions due to their high play/ban rate. One thing to know is there are one tricks that have made it to ranks such as diamond or such such as Singed420 (A diamond singed one trick), Heisendong (Heimerdinger challenger one trick) and Tobias Fate (A diamond Gangplank main) to name a few.
- Solo Queue, Ranked Flex, and Normal Draft (If you're in EUW BR or NA) all operate off of the same pick/ban system.
Going into ranked I advise you stay calm first of all. There is little to no difference between a normal summoners rift game and a ranked one minus well the ranking. Be prepared for people to play a bit better as in ranked people will take the game more seriously and thus you will run into people playing the champions they deem their best. If you're tilted try taking a break while it may not seem like much it can help you out a bit. I personally take 10 or so minutes to just chill after a ranked game but thats mainly due to nerves.
One thing that seems a bit odd but is rather efficient is to watch your replays (which is made easier with riots new client however should you not use it I advise a site like Replay.GG). Look to see what you did well and what you could've done better. Along with this watching how other people play will help some of your overall decision making.
This is an odd tip however keep in mind when playing ranked you can dodge quite a bit. Should you have someone in your lobby lock in Janna jungle with say Ghost Heal it's probably best to dodge. For your first dodge of the day you should only lose about 3 LP. This can be a life saver for some games. Best to wait 6 minutes for -3 LP than 20 for -16. Note dodging while in a series or promos will result in a loss for the game and is ill advised.
Edit: One final note is don't be discouraged if you get placed low. Everyone starts somewhere