First of all remember that we all quilt for our own reasons. One of mine is to be able to create something I cannot go buy in a store. As time goes on I try different things, some come out good others not so much.
Don't let anybody discourage you. Have fun! Remember that your creation is YOURS and rules are for sissies. Remember that there have been some wonderful creations that were thought to be mistakes because they did not follow the "rules".
To me quilting is kind of like raising my daughter. I listened to all the advise that everybody had and decided what to follow. My daughter graduated University 3 weeks after her 21st birthday with a degree in cell biology and neuroscience. She is taking a year off before going to grad school so she can go cure cancer. Guess my approach worked with her.
I cut strips for the body of a quilt or binding by the width of the fabric (because that is how they sell jelly rolls and I assumed there had to be a reason) If I am cutting for border strips I cut by the length of the fabric if I am cutting from a piece that is 1 1/2 yards or more long because I will have less strips to sew together.