What operational-security basics should I follow?

Short answer. A stack of small habits: a username you have never used elsewhere, a unique password, the recovery phrase on paper, short sessions, and small on-market balances.

Identity and credentials

Reusing a handle from a clear-web account is how a name gets linked across platforms, so start fresh. Keep a unique generated password in an encrypted local manager, and the recovery phrase on paper.

Sessions and balances

Close the browser after a session rather than leaving it open for days. Keep the on-market balance sized to the order in front of you and withdraw the rest to a wallet you control, because money on a market is money exposed to whatever happens to the market.