Great to see new members posting and asking sensible questions about clothing etc. Just a little heads up though......
Proban is not "fireproof" - it is simply a treatment applied to cotton that prevents the material bursting into flames (or melting,like nylon for instance). What the material will do under extreme heat is start to char. If this is happening you are on for some serious burns anyway. Proban doesn't make you "fireproof", or able to wade into a firestorm like Superman.
Overalls are probably more to do with becoming "one of the team" than they are about "fireproofing", if we are to be really honest. Though, don't think by any stretch of the imagination that you are not part of the team if you don't have them - you are, and I know a number of marshals who don't have them.
As a trainee you may well end up dealing with a fire! Which is a good thing, you only learn by doing. The real trick is
NONE of us get so close to a fire to as get burnt and that is all in the training, and experience. It must also be remembered that most of us have nylon based waterproofs, so we'd pretty much want to stay outta the way of fire anyhow.
As for clothes, really it just is a common sense approach. It is possible to overthink it. We are nearing the end of the season, maybe it will be worth spending another few days on the bank and getting a handle on what others do/wear/buy/steal/borrow etc? It's nothing clever, just treat it the same as you would treat any other day out in the weather.
Under my overalls I personally wear a number of cotton based t-shirts, depending on how cold it is. Jeans or similar for below. (and no, despite rumours to contrary, I do not wear my wife's underwear!). If I didn't have the overalls I would top off with a jumper or sweatshirt basically, then a coat. Layers is everything
Just don't clash with flags - especially Red/Yellow
Boots - I just use steel toe capped builders boots - I get from one of those cheap High Street chains. Seem to last about 2 seasons at around 60 days a year. Point blank refuse to pay more than about £20.
Gloves, Welders gloves from Ebay/Screwfix seem OK. Only a couple of quid. Work well, gits if they get wet though. I buy two sets - when one gets wet, swop to the other pair.
Waterproofs, mine basically came from Ebay - think the trousers were a tenner or something, and the Orange jacket about £22 - Google " Hi Viz Rail Workwear" to make a start - there are loads.
Hat (baseball is fine) essential, keeps rain off (especially if you wear glasses), sun out, and hopefully brains in. Plus nobody ever knows what others hair lines are, so when you meet people at a social function, you find yourself continually surprised by such thoughts as, I never knew they were bald, had a quiff, had green hair etc LOL. Unless that person is one HairyDJ, but that is another story....