Closing out games in low Elo(mid-late game)

So lately I've been running into tons of issues with the mid to late game, I usually play jungle and sometimes support, and often I find that i get a huge lead early during the laning phase. After tho I find that it goes down hill and the enemy team seems to catch up and wins.

When I play jungle I usually stick to champs like Yi/WW/udyr who can split push pretty well but i don't find much success with it and when I group with the team, I try to focus the priority target or peel depending on what's needed but we just end up losing.

When playing support, most times i win laning phase with my adc but after that unless other lanes do fairly well. And I always try to ward to prevent teammates from being caught out.

Are their any tips or advice that could help over come this part of the game. And maybe priority on when specific strats should be used?

TLDR: do very early game then enemy team catchs up either through catching teammates out or winning team fights.

Thanks!