If you can create a blog and quickly build a relationship with just 10 early readers, then work with them to pinpoint a challenge you're interested in building a physical or digital product for. Focus next on repeatedly solving that problem yourself, then develop a plan of action for how you can personally help those 10 people solve that problem in their own unique situations as well.
Next, ask these 10 readers to "pre-order" the product from you and work with them through a personal coaching regimen that you'll use to make sure your eventual product has all the necessary features in order to successfully solve their challenge. At the end of this validation process, you'll emerge with a solution that's built on the foundation of genuinely helping your readers.