I have some of those bargain threads and keep them for basting and odd jobs, but I do not use them for real quilting work.
As for the connecting thread: do you plan to use it for the quilting or just for the piecing? I use greys and beiges for all my piecing. I picked a set of the colored thread to match the color values I like to work in. I recently added a larger variety to use in applique and I bought a variegated for top stitching/quilting.