It's about being a lot better than their bot lane, and being able to carry your adc. It wont happen every game, but if you are a lot better than the ppl in your elo, you will climb. If not, and only slightly better, it's pretty difficult. I played a lot of thresh to carry myself, as I knew my champion very well, I had lots of ways to spoonfeed my adc, even though sometimes they wouldn't click on my lantern, but all in all, after roaming, good ward placements, and enough spoon feeding kills, I got out of gold, and eventually to where I am now, in diamond.