Ear protection/ eye protection
Having instructed professionally going on 40 years, I learned the hard way about hearing protection. For the past 20 years I have used Peltor electronic muffs coupled with ear valve plugs.
The electronic muffs can be pricey, but they are wonderful. You never have to "crack" a muff to hear commands or shooter's asking questions. I have run ranges where we had handguns, shotguns, smg's, M-16's,M-14's, 50 BMG's and been inside shooting houses where hundreds of flash bangs have been lit off during years of training.
I have a constant ringing in both ears 24/7, and a substantial high freq loss. Wished I had the Peltor's during the first half of my career.
Also, never shoot or clean firearms w/o eye protection. I have seen several instances where shooter's eyes were saved on the line by inexpensive shooting glasses. After having a student let a recoil spring and guide rod get away from him and shoot across a cleaning bench years ago and strike another student forcibly in the corner of an eye, I have always required student's to wear safety glasses when cleaning firearms also. All part of that learning curve.