So you have a few choices on how to climb, the first time I climbed into plat I did it with siege mages like Ziggs Xerath Jayce Syndra. By winning or going even in lane and just keeping it shoved with good ward coverage I could draw some jungle pressure and have a huge impact in late game teamfights with AOE or Catch potential while stalling out losing games with good waveclear giving my team more chances to win.
I recently got a smurf to plat 5 playing almost exclusively Zed I basically win my lane every game unless its vs Cho Gath and then roam on bot lane to get them ahead. If my bot lane gets dumpstered or I am prevented from roaming because I get ganked a lot of am being shoved on hard I just keep my farm very high and split push until im 5-6 items and draw enough map pressure bot lane to buy my team time to 4v3 until late game where zed gets a ton of free ad from his passive on w and outscales many champs.
As a support you can carry by having hard engage or really strong teamwide peel, Alistar Braum Morg Thresh Leona are all great for this. As an ADC Jinx Kog and Lucian all do well. As top I really prefer split pushes like Tryndamere.
