I can't decide what kind of footbag to buy.?

It all depends on what kind of kick you'd like to get out of your footbag. Footbag response varies based on shell material type, fill type, fill level and design.

For a comprehensive look at how to shop for footbags, see this blog I wrote:

http://blog.footbagpowerhouse.com/?p=3

The Footpet is a great beginner footbag because it is cheap, and has a low panel count (making it easier to perform stalls and delays):
http://footbagpowerhouse.com/index.php/footbags/dirtbag-footpet.html

Mid-range in price, and celebrated for it's awesome pop is the Dirtbag Juice. This footbag is also the IFPA (International Footbag Players Association) regulation size, featuring 32 panels of ultra suede:
http://footbagpowerhouse.com/index.php/footbags/dirtbag-juice-plastic.html

When it comes time to purchase your footbag, please consider us:
http://www.FootbagPowerhouse.com

Best wishes! Let us know what you go with,

Jared