Does any part of the system come on when there's a call for cooling? Do you hear any noises at all when you just turn A/C on? When you say that A/C would not turn on when you reset the breaker, do you have to wait a certain amount of time until it does or has it just stopped working for good?Â
The proper refrigerant charge is important to normal operation of the A/C and you'll have to address the issue of low refrigerant at some point, but to fix the issue at hand I think you should be looking for an electrical culprit: a bad breaker, contactor, bad compressor or condenser fan motor capacitors, bad wiring.
Troubleshooting these parts requires you to work with high power high voltage electrical equipment and if you are not completely comfortable with and knowledgeable about this equipment and lack proper tools, it is imperative for your safety to call a professional HVAC technician.