Don't let subs be your only goal, because not all subs are equal (engaged readers and champions of your work), and subs don't necessarily translate into something that you can do anything with. There are many comics on Tapastic with thousands, sometimes many thousands of subscribers. But their Patreons, perhaps, are making $0/month, because their subscribers don't translate into paying consumers. I have a little under 200 subscribers total on Tapastic after 8 months or so of posting comics. I didn't receive any Staff Picks, and I moderately advertise one of my comics outside of Tapastic but I haven't begun mirroring my comics on Webtoons or other sites yet. However, my Patreon's been growing consistently every month and is doing as well as some comics with a much larger fanbase than mine, which is awesome! That means that I can afford to make more comics and hire more artists, and that's my goal with webcomics. Leverage making good webcomics into building relationships with great artists/people and being able to make high quality print comics too.
Then there are comics like Scurry, which began around the beginning of the year. Scurry already has 9,000 subscribers on Tapastic, has received Staff Picks and Spotlights multiple times, and has a Kickstarter right now that has weeks left in its campaign and has already made over 5x its goal (it's made about $45,000 at the time of this post, and could well be on its way to make $80k+, which is pretty unprecedented for a single volume Kickstarter).
First define what success means to you, and then figure out how people achieve that sort of success, and then pursue that within the best of your ability. That's all. Subscriber numbers, by themselves, are just that -- a number.
That said, I am a little concerned about Tapastic. My views and new subs have dropped substantially over the past month or two, and I've noticed that new comics of solid quality that might've been seeing 50-100 subs in their first couple of months a year ago are now getting like 10-20 subs in most cases before they seem to sort of stall out. I feel like maybe reader retention has dropped on average across the site and that problems with the mobile app has reduced engagement with likes/comments (making it harder to appear in the Popular/Trending sections).
But then I remind myself that Tapastic, while a lovely community and a cool tool (mostly as a web platform, I'm not a big app fan), is just one part of the bigger puzzle of making comics. A good first step into building a community. If you're not lucky enough to "go viral" early on, you just gotta keep climbing and keep your ear to the ground. Maybe a couple of years ago, Tapastic was the best launching pad for new comics. Maybe next year, it'll be an entirely new platform or promotional tool. More likely, success means working across many platforms to build a following (or achieve whatever it is that you want to achieve for yourself!) Stay engaged!