Apologies that you didn't get a reply. For some reason, it doesn't seem to send me notifications, either.
![Think :think:](https://mlparena.com/Smileys/default/thoughtfulpony.gif)
Anyway, you are on the right track! The requirements for getting to the classifieds is "at least 10 positive selling feedback, 4 months of active Arena membership, and be at least 16 years old."
I counted through your feedback and it looks like you have 5 selling/trading feedback. Need just 5 more and you're good to go.