VRC is pretty expensive. I’d say around $5000 for general parts and then about $2000 per team. It depends on the amount of teams you have. As a first year team your costs will be the highest until you end up with a stockpile of parts.
I don’t know what region you’re in but it probably won’t matter. Plunging into VRC will help your students learn skills the hard way before it matters. The first year is pretty hard but better to start sooner than later.
As a coach you should order a competition starter kit as well as a pack of each aluminum kit. If you have a bandsaw or cutting device then 35 longs are economical, otherwise you’ll have to deal with precut sizes. Another important thing to purchase is extra batteries and motors, as well as gearing cartridges.
Note: Vex’s drivers kind of suck. Hex kind of sucks. I’d encourage you to pick up some t15 Wiha precision drivers, a t15 T handle driver, and a ratcheting wrench in addition to the drivers and tools vex provides. They’re available on Andymark.
Note 1: vexrobotics / robotmesh / idesign are Vex authorized resellers. Robosource has some pretty great prices on things like spacers, screws, and additional competition products such as socket head motor screws. (They just released color coded torx drive screws, if you want to jump on that.)
Aside from the above I would purchase some wire stock, smart connectors, and a v5 crimper.
As for the size of the field it can be contained in about a 14x14 space comfortably. If you don’t have sufficient space then a half field or even a quarter field would work.