I also am new to embroidery. I got the PE770 for christmas and promised my swimteam that I would embroider the school's name on their jackets. (32 kids).
I contacted Brother USA and they sent me a very nice e-mail. They recommended to use size 14 needle. The jackets were 100% polyester and had a very dense weave. I did have trouble with the machine embroidery thread though. It kept on breaking. I guess it shredded because of the density. I ended up using 100% all purpose thread and they came out beautiful. Thank goodness, I did not ruin one single one. I admit being very nervous. Now I can play. I just made a lace ornament bell. Used size 11 needle and had embroidery thread which I could not use on jackets in both top and bobbin. It came out beautiful. In other words, try different things!!!
p.s. love my PE770