Vision wins game, this is something you should learn asap if you plan on being a support main.
An early sightstone means an early sweeper, which in turn means dewarding the enemy, which also means giving opportunities for your jungler to gank, which also means removing opportunities for the enemy jungler to gank.
Without vision, the enemy has to play more defensively, miss CS because of it while you apply pressure without fear of ganks because you are prepared.
If you push, apply pressure, you force the enemy jungler and maybe even another lane to gank your lane, removing pressure from other lanes and if they don't gank you, you can bully the enemy bot lane and starve them, effectively removing them from the game.
A pink ward > Faerie charm