I want to start an e-commerce shop with my notion project.
I'm aware of using gumrod but it doesn't give me the UX and control of the purchasing journey that I'm looking for.
I would not recommend creating an e-commerce website like that. There are hundreds of things involved that you will simply not be able to do, track, implement, etc...
Users, payment processing, catalog, product variations, stock and a really huge list.
If you just want to add 3 products and a link to pay, just use Stripe or similar and add a link to pay.