Kim, Hold the fort! Umm thread!
I have used XP Poly which is also called Exquisite now. Floriani thread is probably the one I use most as it matches the design sheets. There is also another drawer of Brother threads that I use for some designs. These are all good threads as are most others easily available.
The Exquisite and Floriani threads have color charts available that have the actual threads on them. I put a small sticky dot beside each one. Take the chart to store (or on-line) when buying more colors. This method has only resulted in one spool being duplicated in the color drawers. My local dealer sells all of these brands with equal success. Yes there is a difference in thread but try a few spools to see if you and your machine like it.
To check the thread to see if it is still good take about a 12 inch piece, wrap in your hands and pull. Does it break easily.
The other issue with thread breakage can be using a wrong needle or using the needle too long. Needles should be replaced about every 8 hours. I had awful issues with thread breakage one day in class. The owner changed out the needle to 80/12 microtex and no more issues.
Do you use pre-wound bobbins? I use pre-wound bobbins also with no issues. They are cheaper on-line than the LQS. There is more thread wound on the bobbin so less bobbin changes.
Sometimes sticky stabilizers will cause issues.
Are you doing OK with hooping techniques?
Welcome to the world of machine EMB!