[1] Stop playing Thresh. If you have a 27% win rate after 15 games on a champion, that is a sign that you need a lot more practice with them. You are having far more success with Bard and Blitzcrank, so I would recommend using them when supporting to climb.
[2] You are playing too many roles and champions. While having knowledge and competency regarding different roles and champions is rather useful, spreading yourself too thin means you are generally at a disadvantage against specialized opponents in their own roles. You seem to enjoy playing support based on your recent match history and you are pretty much guarenteed to get the role in Silver, so I would recommend sticking with that role.
[3] Ward more when supporting. While I only looked at a few random games, your wards placed count was rather low for the game duration considering you have Sightstone. I'm not sure if you aren't using it or if you are purchasing it late, but vision is extremely important.
Generally, I would recommend rushing Sightstone (either before or after upgrading your gold-generation item to second-tier). If you place a ward on the bottom side of mid-lane and near your own lane, you can protect both lanes from ganks and control the bottom river with ease.
[4] Your runes are less than optimal. Your AD and AP page are decent (though not optimal), but your tank page is horrid. For support tanks (i.e. Thresh, Blitzcrank, Alistar), I would recommend using the following page until you have the IP for better ones:
- Quints: Flat Armor
- Marks: Flat Armor or Hybrid Penetration
- Seals: Flat Armor or Scaling Health
- Glyphs: Flat Magic Resist