Hobbs 80/20 is a very nice batting to work with. The batting you choose depends a lot on how close you plan to quilt. Some battings require closer quilting than others. The label on the package will tell you how close quilting lines need to be.
The easiest way to machine quilt, in my opinion, is with a walking foot but making wavy/curvy lines instead of straight lines. The curving lines mean that any small deviation won't stand out to you as a mistake. Make up a small quilt sandwich to practice on. You can make all wavy diagonal lines, or wavy diagonals both ways (which ends up as a wavy crosshatch).
Batting should be cut larger than the quilt top, and backing should be cut larger than the batting.
For the backing fabric, there is no need to line up seams. The traditional method is to buy 2 lengths of fabric, split one of those lengths in half, and attach the halves to each side. This leaves a full width in the middle of the quilt. However, you can vary the backing any way you want. One technique I have seen and liked was to slash the main backing fabric diagonally (not corner to corner, but side to side) and insert a contrasting strip of fabric. Really perks up the back!
One thing I highly recommend is heavily starching your backing fabric before layering. This will cut down on puckers in the back. I use a 1:1 solution of Sta-Flo liquid laundry starch and water. It helps to spray starch the top also.