I want to roll for Hercules to up his NP lv

I believe there will be a free ticket for the 4* story servents later this year.

There is a free 4* ticket givaway during the 10M downloads campaign I think so that's a free one but that's a long ways away.
A class based summoning campaign in a couple of months, but i'd advise against it since he has competition with other 4*'s.
Best and nearest rolling would be, Argatha if you want to wait mid-year.

The Agartha Summoning Campaign 2 around July.
https://fategrandorder.fandom.com/wiki/Agartha_Summoning_Campaign_2

Drake on rate up as well. Very good banner to roll on.