Digital marketing can give the impression that business success is all about numbers and mechanics.

My experience tells me that this is not the whole picture. Indeed, the measurements given by the numbers, and the structures, are all results of and there to serve one end: people.

In the end, I would say relationships are behind every business success I've experienced or seen those close to my experience.

The very minimum ones you'll have as an Amazon seller are:

Customers

How they feel about your product (as it shows up in product reviews for example)
How they feel about your service (as shown in Amazon Feedback reviews)

Direct Suppliers

Your Manufacturer
Product photographer
Designer (infographics; packaging; logo; website)
Freight Forwarder (Probably after a year or so)

And likely it will include at some point:

Mentors/Consultants/Experts

A business mentor/coach
Accountant
Lawyer

Staff

Your VAs (virtual assistants)
Your Customer service reps

Peers

Drinking buddies at Conferences etc.
Mastermind members

And broader relationships including:

Media owners, eg: Speaking, podcast interview, Youtube appearances (like my relationship with White Label Expo for example)
Working with existing brands in a wholesale or agency relationship
Developing business with equity partners, debt partners (like banks)

The ultimate basis for fruitful relationships come from Jay Abrahams's "Strategy of Pre-eminence": a decision to serve the other's needs. Whether that be your customer, supplier, mastermind member, or agency client, the same thing applies.

There's no substitute for competence or experience - so be honest, BUT resourceful.
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