What type of anchor should I buy?

Something like this?

Depends on what you are anchoring into. In mud, sand, or a combination of the two, use a fluke type anchor. Anything else and I have better luck with a Delta plow type.

Tough to say without knowing the details of your boat or what type of water you plan on being in

This may help

http://www.westmarine.com/WestAdvisor/Selecting-The-Right-Anchor