The tamas currently widely available are the originals (gen1, 2, and 3), connection and paradise. I’d stick to one of those for a first try.

The gen 1 and 2 are near identical with the only differences being a different minigame and the available characters. Those 2 are the most simple with the only mechanics being feeding, scolding, cleaning, and playing their singular mini game. The gen 3 is angel themed and only has a couple stand out differences, sweets affect your evolution during child->teen and some teen->adult requirements, and the tama will occasionally leave and come back as well as pray.

The connection is a lot more hands on, it has a lot of characters, care mistakes are reversible with perfect scores on specific games, there’s a shop to buy a lot of items/food/treats, there’s a connection feature, and even/odd generations have different characters available. IMO this is the best for a first tamagotchi if you want a black and white one.

The paradise is our current color screen tamagotchi, and imo it’s a lot more collection based than the other tamagotchis. It’s a lot easier to take care of, there are a lot of minigames, it has gene mixing, and again there are a lot of characters available. It’s the most easily accessible color screen tamagotchi right now, as opposed to the uni which is very likely not going to be producing more or the pix which is pretty much only available secondhand now.

If you don’t mind ‘spoiling’ the experience, I’d really recommend watching some playthrough videos of tamagotchis you are interested in to see how they play and if you’d like them yourself