You have to have at least 100 subs to activate ad revenue for your series, 250 for tips. My artist and I have been on Tapas for about a year, have about 1.6k subscribers between a few different series, and to date we've made... $6.50 from ads, lol. Quite a bit more from tips, thanks to the December tipping event, but overall don't expect to make money from Tapas unless you're premium. I have no idea what those kinds of numbers are like.