indeed, ABD is one of if not the most popular mod in the game, a lot of people duel in it but there are a few other mods worth playing : Boxshu_mushu_v3.tbm and lenshu3ng.tbm. They are also very popular mods
I highly recommend playing a wide variety of mods
by doing so you can grasp a strong understanding of the differences between mods
and you can learn something from each mod to use in another mod.
Depends on your preference, if you like more competitive playing, or plan on competitive, try Aikido, Abd, and such. If you like more layed back mods, or dueling mods, try stuff like mushu, lenshu, boxshu, wushu, etc.
Judo is where I started, and I believe it's a great mod figuring out how things work and learning to transfer ideas between mods. Teaches a lot as you get better with it.
Get a good start with Judo, ABD isn't the best option since it requires a lot of skills, mushu is skill-less you can just go to youtube and get some moves... you can move to aikido but its still like abd with a smaller dojo, but the best mod that you can get a good start off is Judo.