Most early-stage startup founders are either hackers, business people or subject-matter experts, and most teams are laser-focused on building something awesome. When is the right time to focus on brand-building and what's the best way for a startup to use its limited dollars on branding?
The best time to begin incorporating identity strategy into the mix is when the vision for the product is clear. If you can clearly articulate what you are building, the key features, the environment you are attempting to create, and who your target customers are, you're ready.
Here's the good news—quality brand and identity advice and visual design does not have to be very expensive. I've worked with large agencies and freelance experts in the past, and the only difference I have experienced is the cost.
Wishing you much success!