I will suggest you to focus on quality of backlink rather than quantity of submission. If you have backlinks from the sites with low quality sites, your website ranking will not increase.
You can generate as many backlinks as you want but you must give care about the quality of the backlinks. the backlinks you create must be quality backlinks, that is, must be created on high PR sites to get more benefits.
It depends on your capacity, but on an average 100 to 200 links are sufficient in forum posting , bookmarking, listing, and some quality links on high traffic sites is also necessary.
I think you don't have to worry about the number of links your create /day or /month, all you have to be worried should the quality of links, relevance of the domain to your domain and anchor texts used.
Gone are the days when idiot who can read a few articles via Google, do some copy paste work and still call him/her as an SEO person. Basically the most important stuff today is not PR (High PR links ,is not a needed). Quality of website and the website's relevance to your domain are the crucial players today.
I think it depends on your website promotion and sites available for submissions. No of backlinks are not important and no of quality backlinks are important for your website is important.
There is no limit but it is better to focus on quality links so don't go for the quantity just go for the quality. Don't use any tool to build links in bulk instead just create useful and engaging contents so people will link back to you.