This spell will not make you literally invisible, but it will make you less noticeable.
Relax and become conscious of every part of your body. Feel your skin. Relax and feel the photons of light hitting your skin, a rain of warmth over your entire body. Now start repeating to yourself.
Light pass through and around me, nobody will see me. Light pass through and around me.
As you chant (out loud or in your head) feel the rain of photons passing around and through you until you don’t feel them any more.
Bang! you are effectively hidden.