Are you saying that you want the finished quilt to be a simple striped design where each stripe is a different width but the stripe goes from edge to edge?
If that is your plan, there are two methods you can use:
Method 1.
Figure out how wide the quilt top needs to be and purchase the fabric at least in that length.
Determine the width of each stripe and cut THAT width (+ 1/2" for seam allowance) from the LONG side of the fabric (parallel to the selvage).
Repeat for all fabrics and sew the long strips together until you have reached the length you want.
Method 2.
Determine the width of each strip and cut 2 strips of each fabric across the grain (however wide the fabric is ~42")
You can now sew those strips together to make one long strip across. Sew the long strips together just like in method 1 until you have the top long enough.
The problem here is that you will have a seam down the center that may or may not line up.
Option 2 is to sew two separate sets of each strip set, trim the edge of each, nd join them along the center. You will still have a seam down the center, but as long as you sew a consistent seam allowance, it should match.
Hope this makes sense.