This is an easy one, but one I get asked about a lot.
How many links should you build per day?
There is only one correct answer.
As many good links as you can possibly get each day. Period.
There are no exceptions. No buts. I don’t care if the site is brand new or 20 years old.
Google does not care about link velocity.
Notice that I said good links.
If you are using spam like blog comments, profile links, social bookmarks, etc., then yes link velocity matters because the faster you build them the faster you are likely to tip over the Penguin threshold. On the other hand, if you go slow, you will likely never rank anyhow.
On top of the fact that Google doesn’t care how many links you build per day, they also are not going to find all of your links at once anyhow. Some they might find the same day they go live. Others it might take them 3-4 weeks to discover. You can’t control when links will be discovered, so trying to stick to some arbitrary number per day is silly anyhow.