My advice would be to build a simple bike for your first and get familiar with what's involved. Many members are accomplished and talented mechanics with years of automotive and motorcycle experience yet they will be the first to admit that motorizing a bicycle has its share of idiosyncrasies. Mastering those and building a super ride can be a challenge. Start simple and learn what it takes to build a reliable bike then move up from there. Just my opinion; there'll be others.
Tom