This is a subjective question, and will depend on a lot of factors. Will you be going alone, or starting your business with a local Taiwanese partner? Do you speak and read/write Chinese? Do you intend to educate yourself on accounting, tax, and legal issues?
Or, will you retain an accountant and/or lawyer to advise on these issues? Will you employ somebody to help out with marketing and the website? Really, before starting your business, you can learn as much as you’d like… But you can’t learn everything. At the very least, we suggest informing yourself about the different types of business structures and work permits available for foreigners intending to start a business in Taiwan, perhaps taking an introductory Chinese course if you haven’t done so already, familiarising yourself with the basics of Taiwanese business culture and etiquette, and reading a little on marketing (including online marketing) and business management topics. Most importantly, purchase a copy of “How to Start a Business in Taiwan”.