Any good schools for a 91b?

Army Career Tracker has the career map for your MOS. On it you will see what personal and professional development your MOS Proponent recommends for you and at which ranks you should be working on them. This is the absolute gold standard for career progression planning.

Get trained on on GCCS-A for when you become an NCO . Also If you can get it, the 91S Stryker transition course for 91B and H. Don't hand wave H8. This is a money ASI for you and the unit.

Ask yourself - "Who makes this ---- for this vehicle?"
Many of the component manufactories have special schools you can take both hands-on and online including schools which will put you in the running for Senior Non-Commissioned, Warrant and Commissioned Officer. Check them out, do a good job, stay out of trouble and just as importantly you need to inform your chain of command of the course of action you are working towards.

Get as much cross career field training as you can. The more you learn the easier being an X or Z will be. H8 is an excellent identifier to have at any rank.

GCCS-A is a must, super benefits for you career wise as well as proficiency. ASV and striker courses are great but any class that benefits your job is an amazing tool to have. new equipment, MWOs, and as always if you yourself find a way, a tool, a part that helps make the job easier, safer, and more efficient will get you into the army's good graces

Correspondence is good for promotion but we all know those courses are rarely completed with out the help of outside sources. Try to get in the schools that are gonna contribute to your units mission . H8 ( wheeled vehicle Recovery) Hazmat, GCSS-A courses. The more Technical courses you complete now makes it easier on you when you start leading troops .

Try to do as many schools as you can. It doesn't have to be something to do with maintenance. Combat life savers, field san, combatives, air assault and so on. You will also have BLC soon. Look for class that will make you a better solider.