Try different brands of embroidery thread and when you find one your machine likes, bite the bullet & buy a whole set of colors. A set will be pricey but then you will have all those colors that you would never think to buy that will add dimension to your designs (shading etc.)
There are lots and lots and lots of different stablizers, both types and brands. Depending on what you are embroidering on, you may need only one or two types. I get mine from all stitch. The stablizer can make or break the success of your design. Here's a link to the all stitch page. If you scroll down there are several links to articles on stablizers
://www.allstitch.net/department/machine-embroidery-stabilizers-embroidery-backings-for-home-commercial-embroidery-machines-10000.cfm?killnav=1
Take all the classes that your dealer offers. different fabrics like terry cloth, Tshirts, sweatshirts and qulting cotton will all have slightly different techniques (types of needles, stablizers etc.) so if they don't cover this in class, ask your instructor for recommendations.