Privacy
The coin, the browser, the machine. Three layers, each optional, each additive.
The subject of privacy stacks in three layers, and a reader can stop at any layer that matches what they are protecting against. Each layer is additive, and none requires the one above it.
The coin layer
Monero over Bitcoin. A Bitcoin payment is legible on a public ledger forever. A Monero payment is not. If privacy is any part of the reason you are here, the coin is the cheapest layer to get right, and most entries default to Monero for you. Do not fund a market straight from an identity-checked exchange, because that ties your name to the deposit regardless of coin.
The browser layer
Tor Browser at the Safest security level. That turns scripting off everywhere, which closes the most reliable route anyone has to break anonymity from inside the browser. The markets in this directory are built to work at Safest, so you lose nothing you need. Cross-reference the desk article on a first lookup.
The machine layer
Tails, for the reader whose threat model includes their own hardware being examined later. It is a whole operating system that boots from a USB stick, routes everything through Tor, and forgets everything at shutdown. It is more effort than the other layers and it is the strongest. Most readers do not need it, and the ones who do already know why.