What I’ve found to be best with any fish frying I’ve ever done, is this:
Make sure your fillets are relatively dry (patting with a paper towel lightly helps, but don’t over-do it)
then coat in flour in one dish, take it out of there and into an egg-wash and then back into the flour.
Also bear in mind that you can make your own seasoned flour, there are a LOT of seasonings available on the market these days for fish alone, just add these to your flour while battering
I wouldn’t personally use anything too strong with fish, as you still want to be able to taste the actual flavour of your catch.
Adding beer to a batter can add an interesting taste and texture as well, like anything, just don’t over-do it.
Another thing about frying fish is that you have to keep the heat rather low and controlled, regardless of the type of pan and especially if you like to use butter to fry with (I do) , butter has a very low smoke point and will ruin anything that is cooking in it.
When you put your fish in the pan, bear in mind, you are not trying to sear a steak, fish cooks very quickly at high temperatures and will end up with the texture of a Red Band boot, that is IF you can lance it off the bottom of the pan.