I would start out by not playing Thresh. He is a very good champ in good hands. But at lower elos, he is hard to play correctly and efficiently.
I usually tell people to die less, but your avg (at least the 4.5 that I can see) is pretty good.
Ward more..like a lot...like you should be placing your
wards and backing to replenish it every 2-3 minutes as the old ones expire. ANd buy
constantly and place them. And then watch the minimap, so those wards are actually effective. Make sure to upgrade to
when you get
, and then to
at 9. Removing enemy vision is just as important (if not more so) as putting your own wards down.
Check itemization. Just had a big supp item update in this new patch.
Whichever champ you end up with (if you DO switch off Thresh), make sure to use their entire kit. Sometimes people will ignore a small part or something they don't quite get. A personal example is Nami. I played her for awhile and was pretty good. Then i discovered how her passive actually works, and I got quite a bit better.
Basically do anything you can to win. Even small things Play efficiently. Don't waste mana or long cds on silly stuff..like that slight chance at hitting en enemy as they dash over a wall. Don't spend all day shopping. You should be in and out of spawn a few seconds at most. Make sure your team is going for towers (and defending theirs)...not just running all over for kills. THe list goes on and on.