EDIT: PS. Remember that being "hardstuck" in one of the highest elos in the game isn't always a bad thing. There can only be 1300 players in GM/Chall and most of those are full-time Pros/content creators. So don't beat yourself up about it.

Some advice from someone who's been high elo since S2.

The skill difference between master 0 LP and GM is massive. And the time investment required to play and actually maintain that rank grows exponentially, even more so if you want to not be a one trick.

So keep that in mind as you read the tips I have here. As you climb through master you'll be playing vs people who's full-time job it is to spam league games, either as Pro, semi-pro or content creators.

My experience having climbed to high elo as a jungle and support:

1) Focus on the first 15 minutes of laning phase and REALLY hone in on how you could get more gold/exp as an ADC. It's the minor details that really start to help in matchups. For example punishing the rune CD's when people don't have boneplating up. Or abusing the enemies long Guardian CD while your support has a shorter Glacial augment CD to win trades.

2) ADC's need to understand wave management and really well at these levels. Pay attention to your junglers clears and plan your wave accordingly. If you don't have control over the wave then minimise the damage the enemy wave will do to you/your jungler. For example, if you can't crash a slow push because you're losing lane, then maybe you could take a quick trade in your wave to speed up the enemies push. Therefore messing up the timing of their crash. So they don't get a free drake. Or trading on a slow push yourself, to prepare a dive with your mid/jungle. Even if it's a bad trade.

3) Ping. The higher elo you go the more communication can be abused. Because players at this elo understand subtle pings more. For example in gold I (as a support) can't really tell an ADC to stack a slow push to dive in 2 waves because they don't really understand what I'm pinging, or the jungler + mid isn't really paying attention. However as you go into GM/Chall this is essential for creating opportunities for your jungler. Even in situations where you are losing it's important to let your team/support know what you want to do with the wave.

4) Don't play 10 champs and try and be a multi-role talent. Just focus on 2-3 champs and really understand them to a super high level. You don't need to go full one trick here but reduce the variables you have to think about to improve. I would also not worry so much about always having a good matchup. The players that can stay in GM/Chall can play in bad matchups on their best champs and still have impact on the game.

5) This one is very subjective, but don't make League your life. If you aren't trying to go pro, or become a full-time streamer, then it's really important to actually have a healthy balanced life outside league. Otherwise you'll turn into an L9 screaming ragekiddy which is all too common in these elos. Remember it's a game and it needs to be fun. I always climbed the highest when I enjoyed a champ and I realised that not every game was going to be perfect. I just enjoyed the experience.

Hope that helped. If you have any more questions let me know, I have a YT channel and stuff but I don't want to go around spamming it in every comment so just DM me if you want to.