You've gotten some excellent advice here Kathy. :) I don't know what else I can add, except to say that when I teach machine quilting, I make sure my students know that it's ok to adjust their bobbin tension as well as their top tension. (Most of them were really not comfortable doing that as they hadn't had much experience with that) Your bobbing thread should come out easily and steadily when holding the bobbin in your hand and pulling gently with the finger and thumb of your other hand, but not so readily that you feel no tension at all. Practice with that.
Also, different needles are required for different thread weights/types. Keep a nice supply of different types of needles on hand to practice with the different threads you have. Some choices might be Universals in size 70/14, 80/10 and 90/14, a top-stitch needle size 80(110), some "quilting needles" 9/11/14, Schmetz microtex sharp needles 70/10, and Schmetz metallic needle 80/12. And keep a list of what needles work with what type/weight of thread. It helps in the long run if, like me, you forget what worked two months ago. :) It's been invaluable to me.
It's not necessary to use the same weight/type of thread in your bobbin as you are using as your top thread. I love to use "Bottom Line" in my bobbin, even when I'm using a 40 weight thread in the top. It just takes practice, truly. You'll get it. :) I nearly quit many times, but am glad I persevered. It was worth the time and all the muslin and scrap batting I went through. LOL I still make it a practice to try out my thread/needle on scrap fabric and batting before tackling my (or someone else's) treasure. I've had to pick a few stitches out when I've neglected to practice first, and it ain't fun!!