I'm not sure if you're thinking of natives, horticultural curiosities, or crop plants. I would take a little of each, especially things that might be rare over there (such as US endemics of all of the above which are not commonly cultivated abroad).

I think it's neat that you are plannning to take seeds over there. I've always done it the other way around, collecting seeds whenever I go to a new place. I'm sure whatever you bring will be appreciated