You may not be aware, but you actually have a hidden Elo for normal games (if you don't know what that is, it's basically a ranking system). Once you hit lvl 30 proper, you'll drop the last bit of artificial rating adjustment for being an underlevelled summoner and be on your own rating.
What this means is, that you should be getting matched against lvl 30's of a similar skill level to you. It's not going to be exact, but you're not suddenly going to start getting matched against entire teams of players who badly outclass you on both mechanical skills and co-ordination.
As for a support, a support by defenition is a champion that can contribute in a meaningful way with little to no items. You have a support in the bottom lane with your AD carry most of the time. The support lets the carry farm, and wards the lane to protect from jungle ganks. They also protect the carry from the enemy AD and support, or perhaps sets up kills for them. Their gold income comes mostly from gold per 10 items, and they mainly buy aura and team support items like Shurelya's Reverie and Aegis of the Legion. And despite all this, come teamfights they're not useless, because their kit is strong enough to let them still be helpful.
Good support examples are Janna, Blitzcrank, Soraka, Sona, Taric, Leona. There are others out there too, but I'm about to enter a game and these are all the ones that came up off the top of my head.