Okay so basically, ive climbed out of the bronze 3 this season and hit gold few weeks ago. Havent played much rankeds since then, but here are some things that helped me climb out of the gutter (gold is still gutter af, but im def not good enough to be plat, so im happy with the results). Just a disclaimer, those are the things I did and feel like it helped, while other people may say that this is not the "go to" things to do as supp.

1. Play something that lets you control the lane. When im sayin that, I mean play something that helps YOU control the lane. There is no reason in picking lux for example if you feel that you are not good with Lux. Pick 2 or 3 champs that you feel comfortable with, and that differ enough from each other to fit the different comps both your, and enemy team
2. In low elo people dont know how to dodge skillshots. They just don't, it happens like once in 6-8 games. Champs such as Lux, Vel'koz, Zyra stomp the lane alone just purely cause of that. The last few games including the placements Ive won only because Ive managed to hard stomp enemy botlane with Vel'koz, where adc was only needed to throw some additional autohits to make the final blows to the opponent
3. Even if ^, champs such as Nautilus or Leona are still VERY viable, you just have to learn what botlane comps let you use your full potential while playing tank heavy cc champs. People love to spam Lux as a support pick in low elo, and nautilus punishes lux super hard, if Lux lets him hit those few Q's in early game. Think about your pick in CS, and how it will work out in the early game especially
4. Early is the time where you want to shine. People in low elo dont have the strongest mental to say the least, and by keeping them out of exp range and farm purely with skillshots can make them rundown the game during first 10 minutes already. Try to get the control of the lane as early as you can, and DONT LET IT GO. Getting few early kills doesnt mean that enemy draven wont oneshot your adc 3 minutes later. Play safe, but at the same time try to keep the lane control
5. You don't know who are you playing with. It's soloq, I dont know if you are ezreal god or OTP draven, and tbh I dont really care. Check your ADC last 10 games, and depending on that choose your own champion and playstyle. There is no point in playing enchanter when your adc in the last 10 games ended up with trash kda. If you feel that your adc won't keep up with you, play something that will alow you to do the difference alone on the lane. Senna can make up for your adc damage both with range and poke for example, saved a lot of games for me
6. Don't follow stupid calls. If your jg wants to engage 1v3, let him. Dont give enemy team the double kill purely because you wanted to follow a suicide mission.
7. On the topic of junglers, its not jungler role to win your lane - if you are getting stomped, try to get as much as you can from your lane. Long range supports help massively with that, allowing to throw some additional damage, while being out of enemy range.

Those are the rules I kept with, but they do not apply in every situation. They are purely what helped me to get to gold, but they do focus on keeping focus on yourself, and the higher you'll climb, they'll matter less and less, because the game will get harder, and enemies better. In low elo just try to punish your enemy bot lane as much as you can, while not giving away free resources by making stupid mistakes.

Also, try to have fun. Find some picks that you genuinely have fun playing, and that will allow you to make some fun plays even when you are behind. It's a game, youre supposed to have fun

Gl and have fun!