I don’t play ranked atm because every game is pure cancer with idiots who flame everyone else for their own mistakes but I do main supp. My advice would be to avoid supps like vel’koz or veigar. Whether I play supp or adc against them I always win lane. They don’t really offer anything that supports the team (not just adc) and veigar particularly relies on getting kills. Mage supps are good if you’re able to land skill shots but not KS. Tanky supps are good if you can master the right combos. My fave supps to play are those who can poke but also help keep my adc in lane to farm as long as possible like soraka, sona, nami. I also like karma and morgana for poke and protect and rakan is really fun to play and great at engaging. Another good engage champ is Alistar, also Leona. I like playing pyke but I’m just not that good with him yet but he has great CC and poke as does thresh and tahm kench.
It really depends on your play style. I play supp champs I enjoy playing but I also take note of my team comp and the enemy teams comp and their bot lane. I try to play a supp that has good kit for my team. Yeah I can win lane and be over aggressive with a lux, zyra and brand but you get flamed for KS constantly and tbh I got bored or playing them after a while. It also only takes one enemy team gank to put you back in your place lol.
Try different champs and play styles in draft or blind, learn your combos, learn map awareness, where to place wards and clearing out enemy wards at appropriate times and being aware of where the enemy jungler is and also keep note of pings from mid and being aware of where the enemy mid laner is. Your job in the early game is to protect your adc, provide vision for your lane and try and provide vision around the bot side jungle and objectives where you can. In the mid/late game your job is to support the team and engage when appropriate whilst providing vision and clearing enemy wards. Being a supp is tough at times but I find playing a supp that plays for the team has better win rates than supps who just want kills, easy lane etc.
I’m only a rookie and still learning but that would be my advice. I’m going to practice some more on draft until the new season. I’m currently at Silver V on ranked but I barely ever play and I got my rank early in the year when the only champ I played was sona xD and I was still a big n00b back then. I hope to have better results next season xD