Your son will be provided all safety gear needed, wildland and structure as well as web gear when he signs up at his headquarters, he does not need to purchase any nomex or leather gloves.
He will need to purchase navy blue uniform t-shirts and working blues, He should have enough undies and socks to last 10 days or so.
I would suggest he have 4 pair of work pants and at least 3 uniform shirts (some units require employees to be in the full uniform at all times around the station) as each fire season passes he will accumulate more uniform items, I would not advise spending a lot of money right away on work clothes as these are expensive!
He needs to have all of his clothing items with him when he reports for duty, CDF should have given him a new employee packet outlining what he should have and where to purchase his blues and t-shirts.
He needs an out of county bag, I suggest contacting www.hawkpacks.com in Clovis for a good selection of bags for firefighters.
I hope this in some way helps, other CDF folks will no doubt have other advice for you.
Where is your son going to be working? I hope he has a long and happy career with us, I’ve enjoyed CDF and think he will too!