I am not a professional photographer, but because of my profession I have been using earplugs 8 hours a day, 5 days a week, for the last 24 years. Best earplugs for gigs are those that block low frequency and high frequency sounds, leaving the frequencies of human speech less muted. Luckily, most hearing protection gear is designed this way. You will hear better what people around you are talking, better than without the earplugs.
I was careless and so I've got ringing in both of my ears for the last 20 years. It is not fun, believe me. No matter how much it makes you feel you are missing the concert - wear hearing protection. You lose it, you don't get it back!
Now, ear-plugs come in different shape and size. We can not say here what is best for you. Buy a sample pair and wear the plugs for an hour the least to be able to say if you still feel good or not. The kind of shop to find earplugs is a hardwarestore, especially shops selling construction building safety gear. Also shops selling musical instruments should sell hearing protection as well. Notice: Ear plugs are not comfortable in quiet environment. Test the plugs under noise.
My favorite is Laser Lite foam plugs because they are very soft, expand gently and have a round head. Some of my colleagues say it expands too much for their ears, and then they use Bilsom plugs, but those (that we have here) have straight cut head and hurt in my ear. Others may find a sort of headset plugs good, but I hate those things, since every turn of my head makes the cord do a swoooshing sound into my ears. What I'm saying is you need to try these things for yourself.
On general health side, earplugs only protect your hearing, but you'll still be exposed to the power of soundwaves hammering your entire body. Vibrations affect your bones and internal organs all the same. After spending time in loud noise (be it music or machinery) you will find yourself tired even if you had no physical work to tire you. And even if tired you'll find it harder to fall asleep. If you stay awake, you'll find it difficult to concentrate on things like reading a newspaper. It is a stress reaction of your body for having been under extended beating by soundwaves. Earplugs are good for you, but not making you immune to effects of noise.