Well first, our sessions have to fall into one of our tracks (link).

Media buying would go under Digital Advertising - you could potentially talk about the evolution of digital real estate, strategies to create the optimal media package, emerging media platforms and their results.

By landing page optimization, I'm assuming you mean UX design which would be under track Design and Creative. For this, you could talk about emerging strategies, design patterns that lead to success, or new experimental ux page designs.

If you know other people who are interested in the same topic or a broader subject, you could create a panel and lead a discussion on it. For example, an interesting discussion might be the move to digital and how small companies can begin to manage their own media purchasing. Will enterprise media purchasing be as in demand? What are the pros/cons? Whether the move to digital platforms has made media planning more complex (more avenues?)? (btw I don't have much experience in media purchasing...my discussion points might be totally wrong. If so, I apologize!)

This might help - it's our conference schedule from last year (link). You can check out the sessions to get an idea of what they're like.

I hope my answer helped and you can submit! If you know anyone else that's interested in speaking, please pass the word. Thanks!