I notice after having played a lot that I start to play a more diverse champion pool. I play more what I think will be fun at the time and not necessarily something I'm the best with or will be effective in the given situation.
It's like being an artist where you're at that stage where you feel like you've learned the fundamentals, so you try to shortcut them by freehanding more things rather than starting with basic shapes. The problem is that you're not actually good enough to freehand things yet and you still need those shapes to get you to where you want to be, so you find yourself stagnating in your abilities, even regressing and drawing worse art. The moment you go back to basic shapes, you begin to improve again and overcome that plateau.
League is a lot like that, where we learn the game with basic champions like Annie and Warwick, but when we feel like we're good enough, we start playing a more random and diverse set of champions like Shaco, Lee Sin, Vel'koz, etc. The problem is that, while we're much more experience than we used to be, we're not nearly as good with the fundamentals as we think we are.
Go back to the basics. Play simpler champions who hard carry like Annie. Play junglers with hard CC and mobility like Sejuani or Warwick. Play champions that can win by just standing there and beating someone to death rather than "lol420outPlayed" champions like Yasuo, Riven and Vayne.
If you got Gold before, then I know you can get Gold again. You cannot worry about your team. Focus on yourself and applying your own personal pressure around the map as much as you can. Something that's very hard to grasp is that players below Diamond typically don't even listen to advice from other players. You might know that your Riven should build tanky since they're 0-2, but you telling them to grab armor will not make them grab armor. They will almost always ignore your advice.
A bad thing about having been Gold and versing Silver players does have a bit of an ego tinge to it. You're gold, they're silver, so clearly you can just beat them. You might play more aggro, try to style on people a bit too much and go for really ambitious plays and just end up feeding in the end. That can cause frustration and tilt badly. If you're doing poorly, you can often begin to over criticize your allies for doing poorly as well, as if your mistakes are in part their fault. Getting cocky is a big reason why some players stop climbing.
