Many projects like gloves and socks require you to pick up stitches and then continue knitting. Your pattern may call for you to pick up 15 stitches, but you know you’ll have a big gap if you follow those directions exactly. This can be easily fixed!
Pick up one extra stitch at the space where you suspect a gap will form. On your next round, make sure you decrease by 1 stitch to remove that extra stitch. There are many types of decreases, but usually a simple “knit 2 together” will work fine. These gaps usually form in discreet places on a project like between the fingers of a glove or on the side of a sock.