Almost all varieties are good at reducing anxiety. On a rare occasion you can get a particular blend that might cause the opposite (sort of a wired over caffeinated feeling) but it is rare. In general there are two ends of the spectrum. Heady varieties that have lots of upfront euphoria, which is good for depression and anxiety and putting a smile on your face. These tend to be "light" happy, joyful, whistle while you work kind of kavas. The other end are heavier kavas that have a little less of the euphoria and make you just want to go sit on the couch and chill. These tend to be more body oriented, muscle relaxing, sink into the couch. Then there are a ton that sit right in the middle, and in fact almost all kavas have a bit of both. Everyone reacts a bit differently to different varieties so no one kava is "best". Your best bet is try several different varieties and see what works best for you. Some vendors provide sample packs as well. If you stick with some of the more popular vendors on this forum you can't go wrong.
If you want a nice middle of the road kava to get started I would recommend Mahakea from Gourmet Hawaiian Kava. It is a nice all purpose not to heady, not to heavy, anytime, anywhere, kava.