I wouldn't buy a cheap machine, you would just have poor stitching/sewing same as you do now.
Save $$$ until you can buy a good machine. Search for a used, name brand machine.
I suggest Bernina, I have had Berninas for years and haven't had any problems.
I have a 150 QE that I piece with and I love it. I bought it used, about 10 years old.
You should be able to get one reasonable priced and it will last you for years.