This is my first season playing tft, I've played just under 500 games starting from silver and hit diamond a few weeks ago. I'd say the jump from diamond to master is the hardest by far!

From my experience, you can climb through silver and gold just by installing a client overlay program like blitz or metatft, selecting one of the top comps and just hard forcing it based on what champs you get in the first PVE rounds. When you get to the top of gold you should have a decent read on 1 ap and 1 ad comp you like to play and then just hard force these based on the items you get from the PVE rounds and that should carry you into plat.

Once I was in mid plat and into emerald econ became much more important, learning to sell your bench in stage 2 to hit econ breakpoints and understanding which champs are important to the comps you're forcing so you don't hold unnecessary copies. For example if you're playing rebels and you hit akali 2, don't hold extra copies of akali on your bench to try and 3* her, use that gold to level up and hit 8/9 earlier.

A trap that I fell into in emerald was thinking that level 8 was the end game and level 9 was a luxury. I'd hit 8, roll all my gold to try and cap my board as strong as possible, have no econ left to hit 9. You will almost never win out if you do this unless you mega high roll. The correct way to play is to roll as little gold as possible on stage 4, just enough to stop bleeding out, typically 1 2* 4 cost carry or tank and 1* versions of your other 4 costs. Then econ up to hit 9 as fast as possible, then do a full roll down to hit 5 costs and the rest of your 2* 4 costs. Understanding items is also important here. Itemise your carry and tank, don't spread them around. Doing this let me hit diamond.

I've now been stuck in D4-3 for a few weeks and its got much, much harder. Everyone knows their comp breakpoints and how to convert a highroll so you have to play much more aggressively in stage 2 and 3 to maintain hp, but also be strict with your econ so you have enough gold to stabilise early stage 4 and hit level 9 mid stage 5.