Dean’s three rules
Find the contacts who know your bike and pick their brains for advice and the best places to source parts.
Being able to make parts yourself helps keep a cap on costs. Get a little lathe and learn how to use it, even if only for bushes and spacers.
Don’t think you have to go down the time-honoured routes of paint or powdercoat for finishing. Consider getting some of the aluminium stuff anodised.