Great idea! Ordering a sample has many benefits. Seeing the product and the quality can help ensure your customers are going to have a good experience.
However, I would suggest ordering a sample first to see the quality and then using that product for promotional photos or a giveaway. If you ship every item to yourself first, then you'll be doubling the shipping time to your customer which could really tarnish their experience.
Ordering one first to yourself should be enough! The supplier is not changing their processes in creating the product, and you can always have a great return policy in place in case their product quality is not up to standard.
Here is a guide on ordering a sample. It goes step-by-step so you can ensure the quality before you start selling! Let me know if that makes sense or if you have any other questions.