To work out the best cable size for your job, you will need to know 2 variables. First, the current draw (C) through the wire. Second, the distance (D) between the power supply and the LEDs.

This is the formula:

C+D/12

eg: Current: 1A, Length: 1m

= 1+1 /12

= 2/12

= 0.167

ie, recommended min cable size is 0.167mm2

eg: Current: 6A, Length: 6m

= 6+6 /12

= 12/12

= 1.0

ie, recommended min cable size is 1mm2

For 0.2mm cable, see here

For 0.5mm cable, see here

For 1mm cable, see here