Polypropylene is the most cost-effective general tank material. Stands up well to some of the cinnamon and citrus based juices that have been known to crack tanks.
These can be purchased from SmokTek for 510 based devices, and Vapor 4 Life carries the same type for the 808's.
Heres some general "rule of thumb" thoughts on cartos: If you're using a fixed voltage battery (stick batteries, silver bullets, etc), then use the 1.5ohm DC carto's. If you have a variable voltage eGo type of battery, 2.0ohm SC works well. For an APV (ProVari, ZMAX, VAMO), use the 3.0ohm carto's.
For all around "best" performance, a Pyrex glass tank is the way to go. Those will likely be out of your budget range though.
Hope this helps!