For new site you should post not more than 5 links a day. It is safety. And first links should be with high pr. Google likes it.
Google won't tell us the limit to build backlinks per day. But you can't build too many links in a day or your site will be in danger.
It depends on your web-site. if you have a fresh site don not post much. Do everything gradually. Imagine if you are not a SEO specialist and you are an ordinary creator of one or two web projects. Do not make intensive promotions at once. I think even in the situation with some old sites it is better to make several links a week but from domain with high trust, make not so many but unique articles and put to a very acclaimed sites. Do not use only PR 7 and more resources begin with PR2, PR3. I think each month no more than 50 articles and 100 links but it depends on your project.
With a new domain lots of things come into play for your ranking including: - domain age... you need to give it time. Most spammers only have a site for a few months so thats why it takes time. Google wants to see if you are real or not! - how long your domain is registered for (for the same reason as above) - .com, .net, .info?