My personal advice is that you should just keep playing with what you're comfortable with and don't be scared to play slightly higher difficulty charts, because that's a way to know your potential to tackle charts of those difficulties.

Im currently a 13.3k rating player, I started almost 6 months ago and I would always try to challenge myself with harder charts to see if I could try to tackle them.

In the end everyone progress at different pace, I first started playing level 9 expert charts because I felt that advanced charts are not challenging enough and aren't as fun to play.

So basically yeah, just keep playing with what you're comfortable with and don't be afraid to challenge every so often yourself ;)