Legally you must have light on your bike as soon as daylight starts to fade. You need a white front light and a red rear light, alongside reflectors.
If you're going to be riding in the dark then you should wear hi vis clothing to ensure motorists can see you.
The main purpose of bicycle clothing is to protect you from the elements, as we all know the weather in the UK can be somewhat unpredictable!
Regular cleaning, servicing and maintenance of your bike maximises the life of your bike's components and helps to identify potential problems.