I reckon each pilot has to make a value judgement based on a balance of comfort, practicality, risk and cost.
Don't underestimate the importance of looking smart.
If all the flying you do is 12 hours a year in a Pa28, then you may as well stick to your third best street clothing
That's what I have been doing, and what almost all my club fellows do, even those that do 50 or 100 hours annually. Actually even the instructors show up wearing just jeans and a polo or t-shirt. It is one of the things that make me like this club: no keeping up of appearances.
Before reading this thread, I took dedicated flying clothing for an extravagancy, justified by the a/m desire to look smart. I can't help thinking that white silk scarfs do fall under this category. But I had never realised that flame resistance could be a factor.
Very unwilling to look like trying to look smart, I would perhaps consider clothing that looks casual, i.e. that I could also wear on a visit to the village pub, but that does offer some protection in case of a fire. Any suggestions?