I suggest you build it on a breadboard with a copper ground plane, such as
this, to minimize the problem that Mike noted. Use the plane for all ground connections.
If bringing 220V on the board, allow space around all 220V connections (noting connected to adjacent pads) to help the isolation.
And please use a 220V isolation transformer for added safety when working with 220. 220V is dangerous by itself without exposing yourself to possible ground fault electrocution from the 220 mains.