It all depends whether you train with your buddies, or in a club( so you only need dvds to complement your training).
If you're just starting with bjj, and you never trained in a club good dvd to start is Practical grappler (same url).These are pure basics, however, basics are always the most important. Mario Sperry has several videos, they are all good and you cannot go wrong using them. Nothing fancy, but stuff that works.Although his sport BJJ series is addressed to advanced levels, they're very clear and everyone could benefit. Although Mario covers takedowns in his tapes, I recommend you take Darell Gholar videos ( takedown for vale tudo and 9-7-5 of wrestling). I have to mention Stephen Kesting- his grappling instructionals are great- very clear and lot of details.
There are tons of istructionals out there, what exactly are you looking for?