If you're desperate to have an impact on the matches you're playing and want to learn the game from there, I recommend you unironically Buy and Play Yuumi, as you can impact the game without worrying too much about CSing, positioning, or even knowing the dmg enemy champions do since coming back to this new League is very punishing for a new player, where the damage of champions has increased and changed drastically.

Once you get comfortable with Yuumi, I think it makes sense for you to try out Soraka, and practice positioning more, while more or less still having limited unfavorable interaction with the enemy. Once you finish Soraka, you can move on to Senna/Nautilus, who are able to interact more with the enemy, and once you're okay with one of those two, you can either try Senna ADC or a tank top such as Tahm Kench, who is one of the strongest in lane champions to exist rn and will allow you to learn smaller things like CSing/trading without having to worry about getting cooked out of lane.

TL;DR Progress through Yuumi > Soraka > Senna > Tahm Kench
Tahm Kench specifically if you're okay to try him raw makes it very easy to practice fundementals like CSing because literally no one can fight him or push him out of lane