[@Silver Carrot] Don't worry about the tags is what I would recommend. There are plenty of Rp's in the Casual section that can pass as Advanced, and may more that one would think should be shifted to Free. Don't worry about who you think you can hang with as far as skills go, if you really want just jump in. You can learn along the way and most GM's are open to Rpers wanting to stretch their skills. It's the try factor that matters. I've seen plenty of Rpers start off in an RP and who posted, in their words, like shit. I've seen those same people grow as they keep trying and learn from their mistakes. Thing is they took the first step. 

I've taken a look at your posts, you aren't bad. If you want to grow to be more what you believe is an "Advanced" Rper, find a group that you think you can work with and join in to learn from when you are ready. There will always be a door open somewhere on the forum for those that want to learn and try something outside of their comfort zone.