If you've been at this a week and only have one subscriber, that honestly sounds pretty normal! Outside of Tapastic it's harder to say when I first got new readers, but I do know I had posted around 40-50 pages of my first comic before people other than my friends started commenting.
I often tell people not to worry about their subscriber numbers until they've been updating pretty regularly for at least a year or two. Before that point, you could be doing everything right and still not have many readers just because they haven't found you yet, and if you're doing all the right things already, there's nothing you can do to change that other than keep going!
Also, this is a small forum etiquette thing, but the forum might start limiting you if you reply to a bunch of posts individually all in a row. A good idea if you want to respond to a lot of people is to do something like this:
@itzewulf - [answer to one post]
@shazzbaa - [answer to a different post]
(if you type "@" and start typing the person's name, the forum will usually suggest people you might mean, so you don't have to type the whole thing out) and then you can just do this for every person you want to reply to in the same post!
or you can quote people by selecting text in their post and then clicking "quote reply," so you get something like this:
and then answer their post underneath!
That way you can answer multiple people in one post, instead of replying to each one with a separate post. :>