BJJ usually borrows throwing and tripping techniques from judo and wrestling. With the exception of guard pulls, there are very few jiu jitsu specific takedowns.
In this video, I demonstrate what I consider to be one of the best jiu jitsu specific methods for getting an opponent to the ground.
I also how you can string multiple movements together to make drilling this particular BJJ move more effective.
The Fundamentals of BJJ, including throws and takedowns, are covered in The BJJ Building Blocks course by Roger Gracie Black Belt Nicolas Gregroriades