Marketing materials means photos, demo reels, headshots, etc.

For modeling, you just need to bring a few pictures (non-profesional is fine) - at least one headshot, one profile headshot and one full body shot in either fitted clothing or a swimsuit. Write your name and contact info on the back in case they ever get separated from your application.

If you are looking for representation as an actress you need to bring a professional headshot (amateur won't cut it in this case), your resume and your demo reel (2-3 minutes of acting work you've done on a CD-Rom/DVD). If you don't have this, you are in no way ready to be represented by a talent agency for acting - these are the minimum requirements for any agent to consider you.