Nah theres no where you can buy it cheap because once you have something on your LOL account say a skin or champ, you can't sell it to anyone, it is yours to keep.
And trust me, you don't want to buy an account or anything, what you want to do is use your first 30 levels on normal levelling up, getting to know EVERY SINGLE CHAMP and i mean every single one, to be good at the game you need to know what every champ is capable off doing. I got 500 normal wins before i even started to play ranked, even though i was level 30 way before that. If you don't know what champs can do you will really suck at the game.
However you can buy riot points though, which you can buy champs/skins with so there is that you can do. @(you need an account to see links)
I would say add me in game, but im on the EUW server and i'm guessing your on the NA