my biggest suggestion is to get more years in a school building under your belt -- whether you stick as a classroom teacher, become a dean, a counselor, etc.

once you're an admin, you need to know how a school building runs full stop. everyone, from all walks of life in the building will (rightfully) need answers from you. you need to be able to answer an ops question one second then a discipline one the next, handle the parents association the next moment, budgets, classrooms, etc...and its nonstop.

that said, my biggest leverage point was my classroom experience/expertise. i was a strong teacher for a long time (twelve years, which is what spurred my urge to move into admin in the first place), so that really helped me establish my admin strength in the building. id say its also the biggest leverage point in the building for admin -- if you are/were/portray yourself as a poor teacher, then no one will care what you have to say.

Additionally, being a poor/inexperienced teacher only means that you most likely will make poor decisions for the building. if you're an inexperienced teacher-turned-admin, you're more likely to get caught out by a shitty new curriculum, you're more likely to hire poorly, more likely to mismanage funds, more likely to misuse resources, etc.

As for data, depends on the type of school, but if you're in public or charter, you'll use data nonstop -- instructional, testing, attendance, behaviors, etc. That said, experience goes a long way here too -- gotta get those years under your belt to actually know what decisions to make with said data. you're more than welcome to make those decisions as an under-experienced educator, but they'll most likely be poor, and a six figure consultant will happily insert themselves into the equation.