Before I started MTS (wich was the tool i was looking for to learn techniques and get an idea of a whole system) my primary source was youtube. I have found like 50 YT channels, many of them show Gi-techs, of course. After discovering 10th Planet and deciding to dedicate to the system, MTS and the enlisted videos in the Technique Guide got my number one source.
I have access to the gracie Combatatives programm and once a month they give out one lesson out of the purple belt track. These lessons are pretty nice, many details and always focussing on the basics, but i would not pay a cent for these videos, they are ridicoulusly expensive.
A friend borrowed me a book from saulo ribeiro, its called "Jiu-Jitsu University" i think, it covers many techniques, starting with fundamentals for the white belts up to stuff for the blackbelts. But, nothing that boosted my performance.
So for me, the source which gave me the strongest push was MTS, without beeing a bootlicker. If you want to be good at 10th Planet JJ, i would say you have to study that system. I think nothing beats training, drilling and work on specific techniques or submissions in sparring, but to supplement this the 10th Planet books, DVD's and MTS should do the trick.
If you want to i can copy the list of YT-channels, but the amount of content is overwhelming and also not sorted in any kind.
Watching big tournaments is a nice thing to do, so you get an idea of how these fighters approach a fight and on wich techs they focus. Watching yourself roll is also a good tool, so after the session you can see your mistakes and the things you're good at, of course.