A good point to start is simply by using the default parameters based on my Gaggia CC and the perform PID autotuning from the web interface. Don't forget to save you parameters afterwars!
Target Temperature: 94.00
Threshold for adaptive PID: 1.50
normal PID: P/I/D 115.00/4.0/850.00
adaptive PID: P/I/D 100.00/0.00/0.00
Target Temperature: 100.00
Threshold for adaptive PID: 1.50
normal PID: P/I/D 91.00/0.26/7950.00
adaptive PID: P/I/D 100.00/0.00/0.00