I agree with the other comments, if he must have shoes then you should get his feet measured properly.
However although babies look cute in mini versions of grown-up shoes, the main function of shoes is to protect our feet from the surfaces we walk on, so if he is not yet walking he doesn't really need shoes. If he is walking, barefoot allows children to experience different sensory stimulations and helps to exercise the small muscles of the feet and toes.
First shoes should be chosen carefully because poor fitting could lead to foot deformities later. Growing feet need room to grow. Shoes should be soft and pliable and fit securely onto feet. Choose a pair with laces, strap or some other fastening to hold the heel in position. The inner edge of the shoe should be as straight as possible, and the toe should be both wide and deep enough. There should be no pressure on the little toe, and the heel should fit snugly.