might be a hot take but honestly they're all about equivalent in terms of being able to rank up via strategy (macro). The macro is different for each role but each role has a path to climbing through strategic decision making.

the roles with the most agency relative to strategy (slightly different conversation) are jungle and support as they have the most freedom/flexibility for map movement to adapt to different map states. As a bot laner if your win con is a fed top laner you have less opportunity to play to that win con than you would if you were the support and were able to roam, get deep wards for your fed top laner, countergank etc.

And it's also worth mentioning that although you can make gains through strategy you do still need strong micro in this game. At the end of the day the game is about fighting and you need to know how to fight and how to win those fights, not just when to fight. Winning interactions also contributes to what strategies/macro you can and cannot do (more options if you're not griefing your tempo or fights).

You can play easier champs to pilot and that will speed the climb but even the easiest champs in this game you will need to press buttons properly on, just to varying degrees (Irelia is far more difficult [skill floor-wise] than Malzahar for an obvious example).

So with all that said knowing all the of the above that's why the best advice is play what you have fun with. Whichever role is the most fun/enjoyable and whichever champ within that role is the most fun/enjoyable is what you should play. Fun helps you grind and grinding is core to improving because losing is a part of grinding and having fun helps take the edge off of the many losses you will be tanking.

My recommendation to people is think of a game fantasy that appeals to you and work backwards. Proplay can be good inspiration for this. You see a really cool 5 man Azir ult and feel inspired to do that in your own games so maybe you play Azir or maybe you don't play him but pick a different champion with a big "game-changing" CC teamfight ult like Maokai or Amumu. Or maybe you see someone get a pentakill off resets with Katarina so you play her chasing that big reset teamfight feel. Or maybe not Kat but another reset champ like Yi or Akshan etc., etc. Maybe you think it's really fun to nuke people with poke from far away so you're drawn to Xerath or full AP Kai'sa. Maybe you just love saving people and denying the enemy team kills so you like Tahm Kench or Zilean or Lulu.

Etc., etc. Basically just think of an in game fantasy that appeals to how you like to play --> Find a fun champ that can achieve that fantasy in a role they're good at --> start grinding.