First to remember, a good gel moisturizer should blend into your skin very easily.
You don't want the gel or lotion for dry skin you're using to stay clumped on goopy on your face, on top of the sweat and humidity that summer brings.
Your choice for best gel moisturizer for dry skin should also last for a long time.
Your skin will be parched and in need of hydration, so you'll need a hydrating gel moisturizer that will serve that purpose for a good while. The moisturizer you choose should survive the sweat that your body produces, as well as not evaporate on the spot after application.