Lighting... so you can see and be seen is pretty critical and if there is not a lot of ambient light you can actually get away with lower output but a 3 watt / 250 lumen system is usually sufficient for seeing. MY PB 2 watt headlight is actually quite practical as a night time driving light (almost matches my 3w Lumotec) and costs $34.00 but ymmv as we all have different night vision.

A reflective vest is some of the best money you can spend and these glow in the daytime too... I never tour without mine.

Reflective sidewalls are one of the best things ever... and good tyres will prevent more flats and make the ride more enjoyable.

This was taken under fairly bright lights...