Is it better to sell one product or many?

One to start, several to stay. A single product is far easier to explain, advertise and be known for; a single product is also a single point of failure and leaves nothing to sell a returning customer.

What decides it

The workable shape is one product that brings people in and a small range around it that they buy next. That is a catalogue built from demand rather than from a supplier list.

The part that gets skipped

Most of the money in ecommerce is made in unglamorous categories bought regularly, not in the ones that photograph well.

Selling online is not passive income. It is a business with stock, customers and a support inbox, and anybody describing it as passive is selling a course.

The number that decides whether a store works is not revenue, it is what is left after the cost of the goods and the cost of getting the customer. Plenty of stores with impressive revenue make nothing.

Where an app fits

This is where an app earns its place — it exists to make the second and third purchase easier, which is where the profit is.