How many backlinks do you consider too many back links per day where Google may red flag you for spamming or performing Black Hat SEO tactics?
It depends on the site authority. If your website is newly born, then I'd suggest you to only focus on quality link building such as guest posting and video marketing on authority video sharing sites. on renowned blogs related to your niche. Avoid low quality article directories, web directories, social bookmarking, profile and wiki links.
There is no limits when it comes to backlinking but consider related authority sites as a priority for building reputation for the site.
technically, even one created backlink to manipulate search engines would be a violation... google wants you to earn your backlinks, not go out building, spamming, etc...however, I doubt google will penalize you over 1 backlink...I would keep the numbers between 5-10/week, build your links slowly, and through authority backlink sources, and avoid using automation. If you do include automation, then send those links to a web20 page that links back to your money site.... web20 pages are more flexible in dealing with incoming links, however, treat your web20 page just as delicate as your own site, as you do not want any of your pages penalized....The good thing about web20 is that you can create many pages, spread links around to do those pages, and over time, seo flows down hill, thus improving your ranking to your money pages. Seo/linkbuilding is a time consuming process; What you do now can take weeks or months to filter through..... also show google that you are active by using social media...If six months go by, and you are getting backlinks...google will be thinking how you are getting backlinks when you are not using social media ie: no one is talking about you...Even more so if you are getting authority backlinks, but yet you are not involved with social media, and google is like wtf is this... If your site is new... I would wait 3 months before building light links... I would wait 6 months before building authority links.... During this time, focus on building quality content...