if you live in a city, head down to your local drum shop, (or electric guitar shop) who will sell a wide range of earplugs, advise you on the different sorts, and even give a rough guess of what size you need! Then buy whatever is around £20.
I have the expensive moulded ones, which are amazing, but probably best to start with the cheaper ones. It’s really worth protecting your ears though! You’ll be surprised how much better gigs sound with earplugs in. The bass will still hit you in the chest but you’ll be able to hear a lot more detail when the ripping distortion is toned down. And occasionally, when you go ‘i wonder how loud this gig really is’ and take them out for 5 seconds, you’ll realise just how much you’re probably damaging your ears without them!