You said you know how the ranked system works but a lot of people aren't aware of the elo pendulum. For a number of games, up to around 40 max, then you will be placed with lower ranked people. Hence why it is easy to suddenly shoot up or down in rankings. Winning games vs higher ranking enemies and not losing to lower ranking enemies is the key to permanently raising you average ranking.
Going about this is quite difficult though. On the bright side good support mains have a tendency to break free of bronze and silver.
So a couple pointers, stay focused and follow the fed ones. If there is that 3/0 draven who is grouping mid with 2 others, try and get everyone to join in. Remember it is better to have your whole team working towards a decent goal than to have some people split off to do better goals.
Playing "go in" supports is very effective at lower elos. Just hitting that talisman button in the middle of your team is often enough to start that full team headlong charge. Is head on charging the best idea? Usually no, but if your whole team is doing it then your team is coordinated and that is good.
Learn to shotcall and prompt your jgler to help out laners that are getting frustrated, or even go yourself!
As a support your real job is to get everyone happy and working together.