I second Montoso Gardens. Amazing prices, incredible selection. I recommend a Trinitario variety to start with, good flavor and relatively easy to grow as well as having the best pulp to seed ratio. For much finer chocolate, a criollo variety with white seeds is superior. Forastero/amelonado is generally resistant and has good harvests, but is mediocre quality at best.
If you’re interested in a genetic portfolio of cacao varieties, then the answer may be different. There are some crazy varieties out there-I personally have this amazing Pentagona variety with a weird pod shape (ridges instead of furrows). I also have some Nacional plants if you’re interested in plants, if you want seeds Montoso Gardens is best for all your standard varieties and even some crazy ones.
Try the Colorado Trinitario from Montoso, it’s a huge pod and has nice colors, as well as tasty pulp. Perhaps also get either a Criollo if you’re felling adventurous, or an amelonado for some more dependability/“regular” cacao.