Mainly it depends what kind of ads you ran for the campaign. If you're working on the competitive niche then it will be
quite tough to make it into profit.
Teespring converts best with facebook ads. A guy ran campaign on Paul Walker, it was a simple shirt with a text.
That guy sold over 150 shirts just in a period of 4 days.
Another trend was at peak known as "Duck Dynasty", a guy sold over 2000+ shirts just in a matter of time.
Find the hot trend, make shirt on it and you will be selling well.