Don't buy lots of anything until you find out what you like. This goes for thread, backing (aka stabilizer), and even designs. Start with embroidering stable woven fabrics before knits since it is so easy to stretch the fabric out of shape on knits. Embroidery Library has some great tutorials about embroidering on different types of fabrics, and it is worthwhile looking for them. Accept the fact that different fabrics need different backings, and you will need an assortment. For thread, it is important that you try a couple of spools of any thread brand before you buy a complete collection. Your machine (or just your preference) may not like one that everyone else does!
Enjoy! I started 20+ years ago with a little 4x4 design space and now have a 12 needle pro machine. It is very addicting.
Pam