There have been a few threads about this, but there's always room for another.
For the bulk of my flying I wear a Nomex suit (or at the least, cotton trousers and a nomex or leather jacket), plus usually thin leather gloves. Leather does the job nearly as well, and pure cotton isn't too far behind.
A few people do take the mickey - which is entirely their problem so far as I'm concerned.
In that utterly freak accident that I can't predict, it may well save my life, or at-least my long term wellbeing. The rest of the time, it protects my clothes, has pockets in all the right places, and I can leave all my flying bits in it when I take it off and sling it in the car after a flight.
(I did a long trip for business today and did just that, flying suit left in the aeroplane, suit jacket back on, job done.)
Military ones are cheap but, well, very military - easily bought on eBay or the like. There are various suppliers in various companies who will happily supply you with non-green ones, but just avoid Polycotton.
Incidentally,watch the video at the bottom of
this page for the Nomex versus polycotton argument.
To not have the p*** taken out of you, the biggest rule is never put any badge on it you didn't earn, unless it's clearly being humourous. The next rule is simply not to wear it unless you're near to an aeroplane, or about to be. Those two generally do the job.
G