Unsure on new champion

Im looking to pick up a new champion but I am unsure on who to buy.

Im Bronze 2 (placed B1 but a series of bad games led to demotion) I main Jungle/Support. I find myself to be a very passive player. In team fights i like to be the peel for AD/APCs or sacrifice myself so others can live. I prefer to get the assist and to push turrets over team fights.
Im not very good with 'All in' Champs

I play:

Top: Nasus, Pantheon, Teemo, Warwick Jungle: Lee Sin, Rammus, Amumu, Xin Zhao, Eve, Udyr, Pantheon Mid: Veigar, Twisted Fate ADC: Caitlyn, Lucian Support: Braum, Thresh

TL;DR: Need help picking my next champion.