1. It depends on the age of your website. If it's a new site, then you can try to create two or three backlinks per day and you need to make sure these backlinks should be indexed by goole.
2. Regarding the second question, more backlinks don't guarantee higher rankings in search results. There is, for example, a
coupons website I have visited before, it has more than 2,000+ reference domains and millions of backlinks, but only gets no more than 4000 unique visitors per day. Based on my experience, only quality backlinks can improve your rankings - backlinks from popular sites, active forums, blogs that users really like. For example, you post a topic on an active forum relating to your niche, if it gets many clicks and replies, you will see a dramatically rise in your search engine rankings. Backlinks from blogs (sponsored blogs, guest blogs, your own blogs) also have a positive effect on your site's ranking position, since it takes energy, time even money to create a blog.
Hope this helps