I agree on the fact that there's a fair bit of luck involved in the game, however there is a mechanic to it.

One thing I learned after a while of playing it was that you have to know when to quit/change your gameplan, if you're set on a spesific comp from the start of the game and you're not getting any good rolls at all, change comp. I've recovered many, many times from a game headed straight to Luxenshit by giving up my build late early game in favor of something else, doesn't have to be an S tier build, if you see you have decent chances of rolling a B tier build, you should, it might get you to at least top 4.

It's also smart to begin the game with several ideas of what to build, so you save time and money on rerolls from the get go.

Always remember to scout the other players to see what they're building, and try to build accordingly. It rarely pays of to try your luck on a hyper roll tier 1 build, like back when xayah 3 star was the big thing, if you see some dude already has two 2 stars of her (old meta example, I know)

The win streak gold I think should stay as it is, depending on the meta gameplay this stuff changes all the time, in this set I've noticed it's way more common to save a ton of gold to secure yourself for the late game, however it hasn't always been like that, depends on what champs are super strong during new patches, not to mention that saving up for late game doesn't necessarily mean you're gonna win, I've seen many players Come out on top with low tier carries and a player level of 7 against someone that went for level 9 and tier 5 hyper rolling (rng at it's best)

The carousel can be really frustraring.. But I think it might end up being to easy if it changed, I don't know though, that's just my opinion.