Which products to upload first: not the best ones, the ones people search for
The first instinct on opening a shop is to upload everything, and it produces a week's work before a single order and a catalogue full of items nobody searches for.
The second instinct is to upload the products carrying the best margin, which is reasonable but rests on the wrong premise: it assumes the customer arrives and then chooses.
On a marketplace the opposite happens. The customer searches for something specific, and your products appear only if they match that search.
The right question is therefore not what you want to sell, but what professionals search for. They are two different lists and the overlap is smaller than it seems.
The products worth uploading first are recurring consumables, the ones a professional reorders several times a year without much deliberation.
They have three useful traits: the search is frequent, the decision is quick because the product is familiar, and whoever buys once tends to rebuy from the same seller if it went well.
A first order on a consumable costs the customer little, so perceived risk is low, and it is the doorway that later leads to the substantial orders.
Discovery products — those the professional was not looking for and might find interesting — have their place, but later. They require a broader search or someone landing on your shop, and at the start that does not happen.
High-value equipment is the opposite case and calls for patience. Nobody buys an expensive device from a seller they have never used: that sale comes after the customer has already bought something else from you.
A practical criterion for the initial selection is to start from twenty or thirty items where you are competitive and which you know you can deliver without trouble.
Delivery matters more than breadth. A seller with thirty items always in stock beats one with three hundred of which half are on backorder, because actual availability is what determines whether the order repeats.
Expansion should then follow what was searched for and not found, rather than a plan drawn up in advance. Searches reveal what is missing better than any forecast.
In summary: start from frequently reordered consumables rather than your flagship products, aim for twenty or thirty items always in stock, leave expensive equipment until the customer knows you, and expand by following searches rather than a plan.