Positioning is a big deal when you're most likely the biggest target. You always want to avoid being in a position where the worst case scenario is you're dove and instaburst, which generally means avoiding unwarded areas and staying close to the member(s) of your team who can peel for you.
Really if you just play safe and never get picked off, you can go pretty far as an adc even if your mechanics are otherwise pretty meh. If you can kite/orbwalk well that's a pretty big plus too, but even if you just stand still AAing the back line, you can have a pretty big impact and probably pick up some kills. Repeat until you're huge and terrifying and you can blow down towers/inhibs, just always keep in mind your positioning so the people designed to instaburst you can't. It's easy to get cocky and think you can 1v1 anyone, or to get reckless trying to get a big multikill, but you always need to watch your positioning and where enemies could be.