Training pure judo, as in for judo competitions or kata, will be a waste of time if you are doing it for jiu jitsu. It will give you bad habits for BJJ, and will only cause you to spend extra money. Training judo specifically for BJJ is a much better idea, and this can be done by watching some DVDs or training one on one with a judoka.
As a judoka I can tell you what advantages we have over BJJ players, hence what you should be working on:
- Grip fighting. Judokas are able to dominate most BJJ players in this aspect. Pro tip: start doing all your standup left handed. It will screw with their heads and open up many opportunities for throws. Also, focus on your footwork and off balancing of the opponent. Work on not predicting their movements but feeling and, even more importantly, creating.
- Throws, obviously. Unless you have a lot of time to work on forward throws that expose your back, like morote seoi nage, harai goshi, and uchi mata, your time is best spent working on foot sweeps and sacrifice throws. Although some forward throws, such as ippon seoi nage, and tai otoshi are relatively easy to learn, the ones that in my opinion are the easiest to get good at and the most high percentage are kata guruma, georgian grip osoto gari, ouchi gari, kouchi gari, sode tsurikomi ashi, and especially tomoe nage.
- Dynamic ground work. Being able to go straight from standing to an armbar against a grounded opponent who has turtled or is attempting to play an open guard is a definite advantage and has helped me many times. Working submissions out of kesa gatame is something that most BJJ players are unfamiliar with as well and will catch them off guard. The Americana using the legs from kesa is an extremely high percentage move for me.
Just focus on those, don't turtle up, and you'll definitely see your BJJ improve!