First of all, the clerk in the store is a nitwit.
Secondly, your top is lovely.
Now to the quilting: A lot of it depends on what batting you use because it dictates how far apart your quilting lines can be. (You can always go tighter than the max). I agree with Ps150 that Stitch in the ditch is a good beginner quilting style. I still do many of mine that way. Yo can easily identify the seams you want to SID and then go for it.