Buy a plain cotton muslin in the 3 to 5 oz per square yard range when you need a first fit check for a woven garment, and move up to about 6 oz for pants, jackets, or bags that need more structure.
Look for a fabric glue that dries clear, stays flexible, and reaches handling strength in 5 to 15 minutes, with full cure within 24 hours. That default fits hems, appliqué, patches, trim, and quick repairs where sewing adds more time than value.
Check a straight seam on two layers of cotton, a folded 1/4-inch seam, and a smooth low-speed start before you pay. If you sew only hems, repairs, and pillow covers, stitch quality matters more than stitch count.
Oil an all-metal mechanical sewing machine after about 8 to 10 hours of stitching, and place one tiny drop only on the metal points the manual names. If the machine is computerized, sealed, or labeled self-lubricating, skip owner oiling unless the manual lists a service point.