Although I participated mostly in FTC in my high school years, I'd recommend starting a VEX team (or multiple ones if it gains interests) because of its affordability, ties with PLTW, and higher chance of being competitive without having a significant amount of resources.
FTC does allow much more flexibility (in material usage), has higher power motors (but also fragile), and have relatively more scholarship opportunities due to ties with FIRST and FRC.
Here are a few links (from vexforum) that has lists of what to get from being a new team to being competitive:
https://docs.google.com/spreadsheet/...haring#gid= 0
https://docs.google.com/spreadsheet/...=sharing#gid=0
https://docs.google.com/spreadsheet/...=sharing#gid=0