Start filling your shelves with reading material before you start to fill your bag with gear. The fist book you should by, and read, is The Tree Climber's Companion. Anyone who doesn't know everything in this book should stay on the ground. Its chepaer than any biner you'll ever buy and more likely to save your life and extend your working career.
Leaern from as many climbers as possible. If your instructor hasn't learned anything new in years, ther's no way that you're going to learn any modern skills.
Get a free subscription to Tree Care Industry magazine from the National Arborist Association:
http://www.natlarb.com/
Buy, and read, Don Blair's Arborist Equipment. Jerry Beranek's The General Fundamenals of Tree Work is another good text to won, and read.
I've talked with many arbos who own these books. But, when I ask them if they've read them the ususal reply is that they've reads parts or looked through the book. That is really hard for me to understand.
Buy a really good helmet with chin strap and wear it whenever you aren't in the truck or on break. Hard hats provide adequate protection but most helmets provide more. The helmet that I wear is made of Kevlar and has a nice shin strap. My noggins worth the extra coin, isn't yours?
Attending any workshop and competition should be mandatory. You expect your car mechanic, veterinarian andaccountatn to be current in their practice, why shouldn't our clients be able to expect the same from us?
Have fun! You're entering the best profession in the world.
Tom