Wiring needs for electrical devices
If you are talking about Romex type copper NM-B wiring for inside walls, then 12 or 14 gauge will be fine.  14 gauge is rated to 15amps at 120V. 12 gauge is rated to 20 amps at 120V.  I don't know how home wiring works in Europe, but if you are at 240V, then the 14 gauge wire should still be fine.  And, pretty much most permanently installed devices like outlets and timers are rated to 15 amps in the US, so in the US it would be easy to find those items which would be suitable.