A first order
Small, cheap, standard escrow. You are buying information about the vendor.
The desk article for a first order. The order is calibration, not commerce. You are buying information about the vendor, and the product is a happy side effect.
Read the vendor first
Every vendor profile states a deal count and a dispute ratio. Read both. It takes about a minute and it is the most useful minute you will spend. A low dispute ratio and a solid deal count on recent orders is what you are looking for.
Keep it small
Smallest quantity, cheapest product that tells you what you need, standard shipping, standard escrow. A first order exists to test whether the vendor's advertised behaviour matches their actual behaviour, so the product is the least important variable. The right size is an amount you could lose without it mattering.
Encrypt the address
Encrypt your shipping details to the vendor's PGP key before pasting them into the order. On entries where PGP is on by default, this is handled for you. Elsewhere it is a two-minute habit that closes a permanent risk.
Let escrow do its job
Do not confirm receipt until the package is physically in your hands, whatever a vendor tells you about their reliability. Confirming early empties escrow to the vendor and removes the dispute path. Cross-reference the escrow topic.