Start now but don't post everything, every day.
Branding and marketing are two of the keys to any successful business. Without a brand (vision, mission and promise), you'll never carve out a niche in the marketplace and you won't be able to communicate "why" when the consumer says "what's in it for me?"
Once you've got that branding piece locked in you can create your campaigns: social media, crowdfunding, consumer marketing, vc and capital...whatever.
So blog now with a purpose. Work on your vision and mission. Then blog it. Talk about what you're doing (and align you comments to the brand promise) whenever you hit an important milestone, or when you can tag into a trending topic or other discussions.
And don't overdo it bc you know, nobody likes spam ;-)