Luck also plays a big role here I think, when you update there are probably tons of other peeps updating, so the possibility to stay at the top of the fresh section is low.
To the forums come mainly creators, so you'd probably get some subs. But the bulk of tapas, the readers, don't come here too often, so that's something to consider, maybe a pretty well known creator likes your comic and gives you a shoutout, that way you get exposure to them fanbase, but, that's again luck.
You can try advertising on social media, readers and creators use them.
Finally my advice (adding to what's been said) is to focus on quality, try to do the best work that you can so when someone catches your comic there'll be more chances to get them interest.
Also, patience, lots and lots of patience.
