You should start practising a few weeks beforehand walking in the footwear of your choice and carrying a pack with weights.
There are no easy answers, but possibilities might include a small rucksack containing spare shirts, underwear, socks, sweater and a raincoat. Possibly some flip-flops or sandals for resting in. Other basics are sleeping bag and mat, towel, washing kit, water bottle, a knife with gadgets, a torch and a small first-aid kit with aspirin, foot lotion and plasters. And, of course, a journal to record your experiences. Most people take a mobile phone.
There is a rule of thumb guide which says that a pack should not exceed 10% of your body weight. Keep it as light as possible but take a few luxuries e.g. books or better still a kindle.
You are strongly recommended to wear bright clothes and “Hi Vis” tags on your rucksack.
You can print off or download maps from this website. For additional information you may want to obtain Ordnance Survey maps or join OS Maps Online (formerly GETAMAP) which allows you to print off Ordnance Survey maps or examine your route online: https://osmaps.ordnancesurvey.co.uk/osmaps/
Before setting off it is very important that you read and understand the Risks, Rights and Duties for those walking or cycling in Scotland.
If you are worried about how much money to carry with you, remember that there are Cashlines in most towns, and many places take credit cards. Your actual costs will depend on how much you choose to spend on food and accommodation along the way.
If you are a regular cyclist your bike is probably in good condition but this is a good time to have a service. If you are not a regular cyclist you should have your bike checked over and start getting in some practice. There are bike shops in larger towns along the route, but you should take repair kits, which at least include tyre spanners and inner tubes. The route surfaces are mainly tarmac or gravel so suitable for mountain bikes or tourers. There are a few muddy paths. You are recommended to wear high visibility clothing.
The Confraternity of St James, which specialises in helping pilgrims prepare for the pilgrimage to Santiago de Compostela, holds frequent Practical Pilgrim Events in London and Scotland. Check this out on