At this point, a great use of your time would be to read the administrative manual, which is already posted on firstinspires. The answers to many of your questions are there. Many more are here on CD - use the search function (OBTW, if you log in you can skip the CAPTCHA questions). For others, ask your senior mentor, other mentors in your area, or post a new thread here on CD.
The most important things a team needs are (some will argue with the order):
- Student team members
- Money/sponsors
- Build site/equipment
- Mentors
I listed mentors last because you obviously already have one. Note that FIRST requires both a primary and an alternate, and the more mentors you have (especially if they have different skill sets), the better, both in terms of managing/inspiring/teaching the team and in sustainability. For your first year, if you can have one mentor focus on logistics and admin and the other on the technical side (but with overlap), you'll do much better than if either of you tries to do everything. (In future years you should spread the jobs even farther.) Teams at 10:1 or worse student:mentor often have high mentor burnout; teams with a 6:1 or better ratio of "full time" mentors are much more sustainable.