When it come to any online following, it's a good rule of thumb to remember that a small portion of your audience will engage with your work and and even smaller portion will be willing to pay for it. If you have a hundred subs on Tapas, I'm guessing about 10 to 15 people engage. Of those people, it's likely that only 1 to 3 people would be willing to purchase what you sell. As your audience grows, so too will the amount for people willing to pay for your work. I personally think investing in merchandise production with 100 followers on platform is more expensive than it's worth, but you're free to what you want. Rather, I think you're better served investing time into research in what people want to purchase and companies you want to work with and saving money to purchase the items you want to sell. Though stickers are pretty inexpensive, so maybe your follwers would be willing to purchase those as is.
Edit: as an aside, its really not about the numbers of followers you have but more about the community you've built and if you have enough time to devote to merch production, marketing, logistics, customer service (for the latter two assuming you're not working through a merch company). If you don't havr time to manage, it wont be as profitable as you'd hope.
