I'm fortunate that I started with a (small) audience, and I'm selling to a focussed crowd. My plugins serve a very specific niche and the producers there are always hungry for more authentic products.
I've never done any paid ads. I might do an experiment on Instagram one day. I see a lot of adverts for plugins in my feed and I'm curious how effective they are.
I sell on Gumroad. They take about 15% fee, then you pay payment processor fees. I haven't done the maths for the total cut but I'd say it's less than 20%.
It's a good deal for me because it includes basic web presence, file hosting, secure delivery, payment processing (cards, Apple Pay, Google and PayPal), email marketing and analytics.
I started selling in September 2022. I'd done a couple of free plugins before that through various platforms like SimpleGoods and SendOwl but didn't take it seriously until later.
When I started selling I posted each new product on my Facebook and Instagram accounts. The engagement was pretty good to start with but I noticed that over time, I got more results from sending emails to my ever-growing email list. When I launch a new product now, I only send it to my email list at first. Then later I post short clips to Instagram but they're supplemental to the email list.
You NEED an email list. They say "the money's in the list" and in my experience, that's 100% correct.
Free products are a great way to build your email list. Most people stay subscribed and as long as you don't flood them with emails, they're happy to receive them.
This is my email strategy:
- Launch email for every new product with 20% discount code, valid for 2 weeks
- Reminder email 48 hours before the launch discount ends
- One email per month with 20% discount off a single product, valid for 2-3 days
That's it. I don't like to bombard my list with too many emails. I'm on some Gumroad seller lists where they send continual discounts, sometimes daily. This would be way too much for me as a customer.
Gumroad includes email marketing, which is a bonus because when your list gets large things like Mailchimp, ConvertKit, etc get into the $100's/month.
I can target emails to people who have or haven't bought specific products. Very handy for offering a discount only to those who haven't bought something. Or offering a discount for a product Y to those who have already bought product X. You can also target by how much someone has spent, so you can offer extra discounts or free stuff to your most loyal customers.
Gumroad also includes extra features like affiliates (having others push your products for a % split), collaborators (where you can split a products revenue with someone else), email automations (for sending drip emails to customers - I don't use those) and upsells (recommended products at checkout).
It does have some downsides. The download links in the receipt emails sometimes don't work and you have to send a link manually to the customer (Gumroad have so far refused to acknowledge this as an issue). I also find their fees to be expensive compared to other services, but for what I get built-in I still think it's worth it for now.
Something else that might be of interest is that Gumroad recently made the source code available, so if there's a feature you want to add and you're handy with Ruby on Rails and JavaScript you might be able to contribute.
This is just an idea.
️ It may be useless
It may already exist
It's definitely already solved by a simple script.
However...
What a great bunch! 
