Compatibility summary
You will need a travel adapter in Gambia; plug types used there differ from Netherlands.
Plug comparison
Netherlands plug types: C F
Gambia plug types: G
There is no common plug type between Netherlands (C F) and Gambia (G). You need a travel adapter.
Voltage comparison
Netherlands: 230V, 50Hz
Gambia: 230V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.