You will want to have someone do it properly. It will need to be vacuumed and recharged. If it just had happened to be slightly low from a very small slow leak, then a quick recharge might have helped. The fact, much more or all was leaked in your situation, you will want the air vacuumed out.But will it damage my system if I don't vacuum out the air? Because if its less efficient then that's not a problem for me, but if it does damage the AC system then Im definitely going to a mechanic for it.
If air pressure is introduced into the system, when you pressurize it up there will be an inadequate amount of refrigerant based on the pressure readings, as well as not enough oil/lubrication of the system. If you fill the amount of refrigerant that the system needs, with the air still in the system, then you will be over pressure.