There’s no magic number and anyone who gives you one is guessing. What looks unnatural is the pattern, not the count. 30 links in a month from a mix of sites after a piece of content got shared is fine. 30 links in a month all with exact match anchors from sites with no traffic is not.
That said, for a new affiliate site I usually do something like 4-8 in month one and ramp up slowly, mostly because budget and good prospects run out anyway.
.
