1. A cast iron dutch oven will cost a bit, but they last years and years. I am using my grandma's skillet that she got as a wedding present back before dirt was invented.
2. I use a breading instead of batter. Seems to use less oil.
3. Keep the fillets in in an ice bath. Then shake off the excess water before dropping into the breading. Cold fish fry better for me than room/outside ambient ones do.
4. Like was said, you can't do a whole lot at one time.
5. If you do get the oil too hot, or it starts turning brown, take a whole tater, cut it into pieces and drop them in the oil. This will clean up you oil and almost take away all burnt smell as well. Take the taters out before your next batch. I normally do this between doing the hushpups and the fish.