A closer matching thread will make all the difference in the world!
Make some practice 'sandwiches' - back/batting/top. Keep the grainline straight between your hands - if you pull on a crossgrain, you'll get puckers and stretch it out of shape. PPP - practice, practice, practice. If funds are a factor, you can use water soluble thread in the bobbin, and when you are done, get the 'sandwich' wet, pull the thread off the top and you're ready to go again when it dries.
Hang in there, and don't forget to BREATHE!!!