Sometimes a fireman's used Nomex or Kevlar approach suit, or a racing driver's old suit is available for a few bucks. Plastics and artificial fibers are very dangerous because they catch fire or melt quickly, and will mix with burning flesh so that healing is more difficult. Cotton, leather, and wool can eventually be absorbed as your body heals. Skin, especially after you work up a bit of sweat, is not very flammable, but it can be scorched and singed. Rayon, nylon, dacron, etc.
Loose clothing is more likely to get in the way than clothing that fits well.
If your hair is long, tie it back. Don't use hairspray or cologne before performing. If you spill fuel on your clothing you must change clothes before lighting up. Even after carefully blotting up spills, your clothing will retain enough fuel to act exactly like a torch. Blotting up spills on clothing may save you from a skin rash, but not from fire.