Starting a project in the round with so few stitches is difficult. if you starting with only 5 stitches, you will have to divide your stitches onto the 3 needles and start in the round on your next increase round.
It might be helpful to work flat for a few rows so that when you join you have some substance to work with. You’ll have to purl the ws rows, and you’ll have a little slit at the center of the work, but that can be easily sewn up with the tail of your yarn.