The best way to learn ASL would be to take formal instruction either from a tutor like here on Wyzant or in a class at your local community college or through adult education classes. I suggest checking with your local community college or university to see if they offer ASL classes and your local, nearby high schools whom often offer ASL classes in their adult continuing education programs. Trying to learn on your own through books or videos can be very frustrating as you have discovered. You do need the feedback you would get from a tutor or teacher in order to ensure that you are making and interpreting the signs correctly.
If you are interested in one-on-one tutoring I would be happy to meet with you and to gear my instruction toward your needs to communicate in the job setting at Long John Silvers.
Regards
Bill Newell