sorry you're having a tough time with it.
Have you printed off a manual and followed it. Have someone else go over it with you...even if they don't sew.
Needle's threaded - right to left not left to right.
Bobbin's Case on left - thread coming to you - put in case - thread comes to you and then goes back. It should fit snug in the grove thing.
check websites for which way the flat side of the needle gets put into the needle holder.
I think the cheat is *NFL* needle flatside left....
I'll bet it's something simple. For $300 I'd keep working on it. If after researching and trying, I'd look into Ebay and PayPal's policies about getting your money back....did the ebay ad say it worked?