Leveling is extremely boring and time consuming, Either spamming 7 min 3v3 games until you want to kill your self or rushing 5v5 bot games for literal days. Heres the easy answer. YUUMI
Yuumi was a meme as soon as she came out for being an "afk" champion. but she actually gets even better. This method wont be as fast as 3v3 games but it being 99% afk makes up for the lack of speed.
Fun fact, Yuumi w on an ally counts as you moving, and you only get kicked off if said person dies or backs. this is easily able to be abused.
Step one - buy yuumi on your new account. (can refund later to buy champs for ranked reqs)
Step two - Lock yuumi immediately in champ select.
Step three - Load into the game, 5v5 beginner bots (runes dont matter, although demolisher would be preferred ).
Step four - turn down all of your in-game volumes EXCEPT for SFX to hear when the champ you are on backs (this kicks you off in the fountain)
Step five - Jump on any of your laners that arent literal bots.
Step six - AFK your way to level 30 one game at a time. tabbing in occasionally to hit w.
EXP boosts speed this up quite a lot aswell.
(sorry for the horrible format, I've never made a guide before)