I have been through that paradox before- on one hand you need to build credibility as a pro and build your brand with your blog, but on the other hand you run into the danger of exposing your naivety as a startup.
The blog can be an excellent idea if your target market is small-business and startups. You see the point. Empathy factor and belief- that you have been through all that and succeeded.
If your target customer-base is beyond SME's and startups than start a normal blog sharing your present expertise, concerns, opinions and views about your industry.