I recently got gold 5.

I am getting trashed on. The only champions I can play and win with are and . I end up feeding whenever I go something other than fizz or hecarim. I can't really practice normals because I either end up against 5 premade diamonds (I get destroyed in 15 mins) or I'm against a bunch of lvl 8 players (I win in 15 minutes). Any tips to help me climb more? (I am still winning most of my games but I can only get carried so many times).