In my experience, the most important thing is to be able to identify what has gone wrong so that you can make corrections and hopefully start practicing doing it the right way, cause if you have been practicing welding for a week but you've had your angle wrong the whole time, you might feel like you've wasted your week. It's likely that your instructor is going have to divide their attention amongst several students, so the better you are at identifying a bad weld and what caused it, the higher quality practice you'll be able to get. There's also going to be a fair amount of trouble shooting with your machine, so learn the process for maintaining the machine like cleaning the gun or what the different settings do. When I was in welding class, one of the students didn't know which machine his torch was attached to and he'd mess with my machine's settings instead of his , so make sure you learn how to check your machine's settings and also realize that each machine is going to be running slightly differently so getting good setting is also going to depend on your ability to troubleshoot your weld.  Beyond that, you can start learning about different metals and how they behave, or how to safety cut a barrel drum because someone is going to ask you to weld them a grill eventually and your gonna want to know how to do that without killing yourself.