To ensure you and your vehicle comply with legislation you should have the following:

Austria 
First aid kit
Warning triangle
Headlamp converters
Hi - Visiblility Jacket

Belgium
Warning triangle
Headlamp converters

Denmark
Warning triangle
Headlamp converters

France
Headlamp converters
Warning triangle
Spare bulbs

Germany
Warning triangle
Headlamp converters

Italy
Warning triangle
Headlamp converters
Hi - Visiblility Jacket

Poland
Warning triangle
Headlamp converters

Spain
Warning triangle
Headlamp converters
Hi - Visiblility Jacket

Recommended products 
Spare bulbs
A fire extinguisher
A first aid kit