There are always a thousand things that you can prematurely optimize (page load time, HTML, conversions, etc). The trick is figuring out what the highest ROI thing is for you to optimize right now given your specific point in time. If you get 100 visits/day set metrics around sign up, retention, or whatever is going to build you up to 1K/day. Then figure out how to get to 10K/day, and so on.
There are always a thousand things that you can prematurely optimize (page load time, HTML, conversions, etc). The trick is figuring out what the highest ROI thing is for you to optimize right now given your specific point in time. If you get 100 visits/day set metrics around sign up, retention, or whatever is going to build you up to 1K/day. Then figure out how to get to 10K/day, and so on.