Find a good site to teach you to double knit and you’ll be cooking with my alma mater! Here is my advice for edge stitches. With one strand of both colors held together, cast on 2 more than the pattern, so 38. I use long-tail cast on. Do not count these 2 extra stitches as your pattern! On the first stitch (which is not really counting as a stitch), hold both colors together in the back and knit through the back loop. Next stitch is stitch number one in your pattern. Do your pattern of 36 stitches. On your last stitch (which is not really counting as a stitch), hold both colors together in the front (as if to purl) and slip that stitch as if to purl. Start and end every row this way and you will have a nice edge.