start with a small practice sandwich- like a 12" square---and work on it until you have it figured out-
sometimes trying too many different things only makes matters worse.
you need to get used to the machine- before trying to quilt a quilt with it.
are you using a free motion foot? or a walking foot?
try to do some basic sewing---piece a 4 patch-
if the stitches are good top and bottom- great- make a practice sandwich and start practice quilting- if the stitches are not ok- start trouble shooting that- first.
if you have been turning dials- & screws all over the place it may take you a while to get it back to where it belongs- but start at the beginning---a 4 patch would be a good place to start