Welcome to the wonderful world of machine quilting. I hope I can help you with your problems as I have done the same thing myself.
First off, how are you basting the quilt? If you are hand basting with needle and thread, you may be basting it a bit too much and the fabric has no room to "move" a bit. If you are using the safety pin method, you may be having the same problem. Your basting, pin or thread, should be about a hand width apart. This will allow you to "manipulate" the fabric under the presser foot if need be.
If I am correct, sometimes you are getting a very small "tuck". I had this same problem when I was quilting on my domestic machine as well. This "tuck" should be happening when you come towards the end of the seam and the adjoining seam has already been stitched. I hope I can explain this so it can be understood. As you STD (stitch in the ditch), look ahead to where you are stitching too. If you are coming to an already stitched seam, sort of stretch the fabric a bit while you are sewing. This should help eliminate the "tuck" at the end. Also, if possible, adjust the pressure on your presser foot. What is happening is your fabric is being pushed a bit by the presser foot.
On the outside borders, you should do them with free motion quilting method. Just remember, if you have any curves in the design, SLOW DOWN on the curves. Everyone has a tendancy to "speed" around the curves, if you do this you will get "eyelashing" on the back of the quilt. That is where the bobbin thread pulls the top thread to the back side and the result looks like eye lashes. You can also STD using free motion and you may not get the "tucks" since you will have little to no pressure on the presser foot.
As far as your sewing machine is concerned. Don't think that if you spend a great deal of money you will be getting a better machine. Example: I bought a machine for $2500 and thought I was getting a really great machine. My daughter thought she wanted to start sewing, so I bought her a $500 machine, same brand as mine, for Christmas. That little machine of hers will sew circles around my machine! In fact, I even tried to TRADE machines with her and she said NO WAY!
When you do go to purchase a new machine, be sure to do LOTS OF RESEARCH, and try the machine using your own fabric and threads! DO NOT buy a machine strictly because of the name brand.
Hope this helps you and please keep me posted on your progress.