According to multiple sources, crochet stitches that have more spacing between them tend to use less yarn. Here are some stitches that use the least amount of yarn:

• Single crochet: This stitch uses shorter stitches and is particularly helpful when creating projects with multiple colors and stitches.
• Double crochet: This stitch is more economical in its yarn usage than other basic stitches and produces much taller stitches than the slip stitch and single crochet stitches.
• Treble crochet: This stitch uses slightly more yarn than double crochet but is still considered to be one of the basic stitches that use the least amount of yarn.
• Solomon stitch: This stitch is versatile, quickly worked up, and has a unique pattern. It is considered to be one of the most "yarn-saving" stitches.

Other stitches that use less yarn include V-stitch, filet stitch, trellis stitch, mesh stitch, granny stitch, and moss stitch. However, these stitches may not be suitable for all projects as they create openwork fabric with visible gaps between each post. When trying to conserve yarn, it is important to think about the pattern and yarn usage.