Looking for what new champ to buy

Brand is a good choice right now with EVERYONE complaining about the TANK meta you do some much dmg off the enemy total % hp so its wise to get him but he is like 4800. Fizz will most likely be getting a buff soon if not already has as he will be getting a new skin and nerfing him before the skin comes out will make no real sense to make the most of the profit to buff him instead.
Lulu is a good choice as she can MID TOP and support( JUNGLE MEH) she can also be a great teamfighter and game changer with her ult and also helps that she can spam Q that does do decent amount of DMG and has long range.

Zac if you want to play as tank for top and jungle. Kha zix if you want to 1 hit people and can be played Top Jungle and Mid( only if you already have a AP champion on team) like rumble top.

Just to name a few

It would help if you told us what kind of champs you like. I looked at your profile it it appears that you enjoy assassins. Assassins who can play all of those rolls some what effectively are