I also signed up for my local fabric store's emails (this is not an LQS..they sell all kinds of fabric, quilting cotton included). This way, I get quick notice of sales, whether in-store or online for their shop and when I go in, I head straight for the discount bins. Often sales include notions, which is a great time to get other supplies such as needles.
Take advantage of liquidation sales, clearance sales, thrift shops, coupons, etc... Thrift shops in my area actually have bins for sewing fabric, so I often just pop in, look and see what's in those bins and leave. It's not time consuming, but since it changes over so often I keep popping in to peek.
Ask family and friends for their clothing when they discard them. Men's shirts and ties are handy.
Lots of patterns are available free on the internet along with tutorials. Youtube is great for those. Check out Missouri Star Quilt Company, they have great tutorials. Any pattern can be adapted to use any color fabrics. Don't be put off by quilt patterns using jelly rolls, charm packs or layer cakes, you can easily make your own from fabrics on hand.
There are online shops with great prices and others have listed those, so make sure to check them out.
Even thread....I buy thread on cones rather than individual spools. Much more economical. Buy neutral colors and you'll be able to use them on any quilt. My fabric store has their own brand of serger thread on spools (polyester). It's dirt cheap, so I bought a spool and tested it out. (I've heard of people trying serger/overlock thread and having issues so I tested before I tried using it in a quilt) I sewed two strips together of fabric with it and then ironed it like I normally would and it was fine. I actually yanked on the fabric, trying to pull the stitches apart and I couldn't. So then I tried to see what the limits were on that thread. I set the iron on it for wayyyy longer than I would normally, on a really hot setting and tried to scorch it and see if it would melt or fail and tested the seam again. Used steam, no steam, etc... The darn stuff is indestructible apparently, so I have no concerns of it holding up for me during my normal use. And it's much cheaper for me than the name brand stuff.
And starch...I make my own starch for just pennies a bottle. I can't get liquid starch here in the stores (only the stuff in a can and I don't want to breathe in those chemicals). Rather than ordering it in, I make my own. Super simple and works great.