If you have access to a JAF where you live, that can be a good place to start. The cheapest fabrics they sell have caused me problems with them wearing out too quickly, but they also sell designer fabrics (typically in cheapy fabrics are along the walls & the designer fabrics are on free-standing shelves in the center of the quilting section) that you can buy when they go on sale or with a coupon. I've seen Free Spirit, Robert Kaufman & other quality cotton fabrics in that section that, when you have a coupon/sale price, are a reasonable price and the same great quality as what's sold in the nice quilt shops. The only thing I sorta dislike about JAF is that a lot of times I get crooked cuts, so now I buy an extra 1/8-1/4 yd of fabric to I can square it up properly.
Beyond that, solids are typically much more economical than prints & actually show off your quilting more. I like Robert Kaufman Kona solids or Moda Bella solids. I will shop around for deals at different online shops including
Missouri Star Quilt Company,
Fat Quarter Shop,
Fabric.com, and
Amazon.com. Amazon is my least favorite because it's basically all re-sellers & I've had bad luck with some of them sending me the wrong product multiple times (e.g., I ordered Kona snow & they send me Bella snow and thought they were "close enough" because they were both given the same color name -- after the 3rd time, I gave up & just kept the jelly roll for a future project).
Hancock's of Paducah is another option that many penny-conscious quilters like. eBay is a roll of the dice. You might get fantastic fabric; you might get a cheap knock-off. Know what the standard price is on the item; if it sounds way too good to be true, it definitely is. Be sure to ask if the photo shown is of the actual product you're going to receive or a similar item. Check the seller's ratings. Make sure wherever you buy from that you know their return policy. Also, if possible, try to either order a color card or go to a local shop to figure out what the true color of the fabric is because depending on the lighting, photography, file size & your computer screen, it may not reflect the actual color of the fabric. I've had quilting friends who've ordered online thinking they were getting a dark pink or deep red & when it arrived they were pale pink & bright red that had been shrouded in shadows when photographed. The one allowed the buyer to return. The other said he would only allow her to exchange it for the same product (e.g., if the pale pink were defective, she could send it back & get another cut of the same pale pink fabric).
I have no idea what B&M is. Do you know where they're located?