Hello Dan, and welcome to the board from another 50 year old man!
You question is a good one and you have received some good answers. Definitely use 100% cotton fabric, and only use it if you like how it feels. Good quality fabric is easily distinguishable because it feels nice, has a good weight, and you won't be able to see through it when you hold it in front of your face. The brands mentioned are all good. In addition, Michael Miller, Timeless Treasures, Andover, Benartex, Marcus Brothers, and Henry Glass are good brands.
As for quantities, if you want to start with squares, I would buy a fat quarter collection and cut it into squares. I have bought collections from Missouri Star and Connecting Threads and been very pleased with them. A FQ can be cut into 12 squares with a 2.5" strip left over, and it will be good practice using your rotary cutter.
Don't feel like you HAVE to collect a stash to make quilts. For your first few projects I would buy what I needed for each quilt with a bit extra fo cutting errors. What you don't use will become part of your stash automatically.
Any time you have a question just post it here and you will get lots of advice. And even though many answers will be different they are probably just different approaches to the same end. Also if you want to post progress pics we would love to see the process.
Most important - HAVE FUN! This is a great hobby!
Darren