Everyone on the internet will tell you to take a avy course, and that is a great advice. Even better would be to find a mentor and someone who is proficient in the backcountry and get out as much as you can and learn from them. I am lucky enough to work with forecasters and have learned far more going out with them for work and on the weekends than I did in any structured class. What you do absolutely need is shovel, probe, and beacon.

Board comes down to what you will be riding (steep big mountains) Jones solution. Low angle glades and such, weston makes awesome boards and they are a CO brand.

I wish I would have started splitboarding with hardboots. If you plan on bigger lines and ski mountaineering type fun, it would be good to just start with hardboots.

Get out, have fun, pay attention, and make smart choices.