This is mainly a build and setup guide for beginners that just want to start ranked games, this is a base that everyone should be aware of, and a knowledge you must have before starting to play ranked games.
Why such an setup?
Because this is the most viable one to play, obviously a setup should contain;
AD Carry;
Any of the following ones work; Caitlyn, Tristana, Vayne, Graves, Corki, Urgot, alternativelly Ashe, but that is one of the most weakest AD carrys IMO.
Support;
Any of the following ones work; Alistar, Sona, Soraka, Taric and alternativelly Nidalee.
AP Carry;
ANy of the following ones work; Karthus, Kassadin, Sion, Anivia, Annie, Brand, Cassiopeia, Kennen, Leblanc, Vladimir, Malzahar, Morgana, Orianna, Ryze, Swain, Veigar, and alternativelly Xerath(?).
Jungler;
Basically any champion can be a good jungler, the list would be enormous.
Brusier/Solo top;
Some people choose to go duo AP, meaning two AP carrys, one mid and one top, this is something most people skip and use top to lane a offtank/bruiser, which can be any from Akali to Yorick.