I love to deep fry my fish using the cooking oil Canola oil which gives it a very good taste and it's pretty cheap to buy and cook with.
I buy the larger jugs of Canola oil at Walmart and deep fry other foods besides fish such as chicken, french fries etc.
Most fish you buy in some restaurants is cooked using Canola oil which gives the fish a good taste and makes the fish really delicious.
Refined Olive oil or just Olive oil is also good for deep frying fish however I just use the Canola oil which is very good and inexpensive as well as being pretty healthy as well.