Support is a very simple, yet tremendously game changing, as well as complicated for the role you have to perform. Wards, simple 75g or 125g item that could either make you lose or win the game (just lost the game). Generally you will want to start the game with Meki Pendant, 2 green wards, 3 hp pots, 1 mana pot. take the same thing but change the green ward to pink for early game ganks (Shyvana, Lee Sin, Shaco, Tryndamere) so you can kill the enemy teams ward for early lane control. Green wards and other pink wards can be spotted by pink wards as well as oracles (talk about that later), so you will want to put pink wards at more crucial parts of the map; Baron, Dragon, Tri-bushes, and river entrances. mid-late game you can grab an oracles elixir to have excellent map control by destroying enemy wards. Another important factor to support is WHERE you place the wards, like exact location.
With this ward placement you can get more vision covering 6 very important locations around dragon. Other important support items would be Shurelya's Reverie, Aegis of the Legion, Soul Shroud, Zeke's Herald and Frozen Heart as well as GP5 items like Heart of Gold, Philosophers Stone and Kage's Lucky Pick. Here's a map showing some key ward placements.
Any questions just comment.