You start to make (or lose money) not when you are selling to customers but when you are buying from suppliers. Look for trusted suppliers.
Ask around in the industry.
The best supplier/s will be those who are willing to grow with you - both working for each others' interests.
Big suppliers may not have enough time for small, first-time buyers.
Too small suppliers may be cutting corners on quality on their way to survival themselves.
You also want suppliers who are in tune with industry changes (or even ahead).
But, never be dependent on one supplier.
Keep backups lined up.