Recently new player from TFT, it took me two seasons to reach platinum.
I used the first season to learn the basic mechanics of TFT. Like traits and trait bonuses, Items and items synergies.
And I used the second season to farm the ranks since I understood it.
Tft is an auto battler so you definitely need to learn the meta builds. I would say that it is 75% luck and 25% memorization.
Go visit the sites like TFTactics or MetaTFT. These sites provide you with the data you need.
Next is to read on the traits. I firmly believe that playing you favoured comps often lead to victory. For example, I would call myself a Disco simp because right now I believe that the Disco trait with a twisted fate carry is a pretty strong comp. I dare say S Tier, so as much as possible I run that for my games.
Next is to be flexible. If you see someone in the board using the same traits and units as you, then you have two choices. If they have weaker underleved units and bad items then you can push forward with that comp, but if they have better levels units and gear then it's time to switch your comp.
Last bit of info is for economy. Never Ever and I repeat EVER spend gold on rerolls or level ups if you are under 50 or 52 gold. You gain extra gold as interest every 10 gold and max is 50.
That's the basics for it, once you reach higher ranks then that would be the time to look into more advanced builds from pros.
Good luck strategist!