does it matter when you submit a new site to a search engine? Should you develop some traffic first, or is there no advantage to this. Should i submit as early as possible and then build up traffic?
I don't think that there is any advantage of first building traffic and then submitting to search engines. Infact, you are going to get traffic from the search engines So, submit your site to search engines.
No search engine demands "this much traffic" for submitted sites... so no need to do it...Submit as soon as your site is ready...
You don't even need to submit your site to search engines. Just finish the development of your site, touch up with on-page optimization or keep it in consideration when making the web pages, then start to build backlinks to your website and the search crawlers will find your website all on their own.
First thing is to make your website search engine friendly from development and design point of view. Follow the Google guidelines for better and easy crawling of website. Then submission in other search engines is plus point.