The first order has arrived: what you do now matters more than the sale
The first order from a new customer is not a sale. It is a test the professional is running on you, almost always on a small amount and on something they do not urgently need.
They are doing it deliberately, and it is exactly what you would advise anyone assessing an unknown supplier. The value of the order has nothing to do with what is at stake.
What is at stake is whether there will be a second order, and the difference between those two outcomes is decided almost entirely by how you handle this one.
The first thing that counts is dispatch speed, and it counts more than the price you gave. An order that leaves the same day communicates organisation better than any company description.
The second is confirmation. A short message saying the order has been received and when it ships removes the uncertainty typical of a first purchase from a stranger.
It need not be elaborate. It needs to be prompt, because the value lies in telling the customer that on the other side there is someone who has seen their order.
The third is packaging, which gets underrated because it looks like a matter of form. A product arriving properly protected says that whoever shipped it knows what they are doing.
With medical devices packaging also has a substantive function, because the professional must be able to verify that the product is intact and the label legible.
Then there is what not to do, and it is where new sellers err most through excess of zeal. Do not turn the first order into a sales contact.
Calling to offer something else, sending catalogues, asking for a meeting: a professional reads all of these as intrusion precisely when they were assessing you.
The moment to ask for a review is after the product has been received and used, with a short message. Not on dispatch, and not alongside a sales offer.
If something goes wrong, how you handle the error counts more than its absence. A seller who errs and puts it right quickly leaves a better impression than one who never errs, because the customer has seen how you behave when there is a problem.
In summary: the first order is a test rather than a sale, ship the same day if you can, confirm with a short message, take care over packaging, do not turn it into a sales contact, and ask for the review after use.