"Julch" (Can't we please use our real names?!)

>>>...have a symmetrical airfoil. Are there any standards to start with?...<<<

I will refer you and this "string" to our rotor blade expert, Bill F.

In the mean time, I would suggest a flat-bottom airfoil, very light construction and if you want to experience true autorotation, begin your attempts accelerating into autorotation using flat blade pitch.