Inspect before comparing
Open the item details and check its slot, attributes and trial-origin label. Compare it with the companion equipment already in that slot. The comparison is about your Play With Purpose character, not the character that completed the ARPG run.
Rarity alone does not decide what you should keep. Read the actual item information and any relevant set information shown by the service. Avoid assuming that the item's appearance or name gives it an effect inside your ARPG.
Separate player demand from a wallet offer
A player listing lets another person choose whether to buy at the offered terms. The price you enter is an asking price, not an instant conversion. An automatic Wallet buy order, when available for the item, is a separate option with its own stated settlement.
A trial item can be eligible for player trading while remaining ineligible for wallet resale. That restriction remains with the item after a trade. Check the detail panel before choosing a listing price or interpreting another seller's offer.
Leave the item in one usable state
Listing reserves and unequips the item. If you decide to keep it instead, cancel the listing where permitted before attempting to equip it. An auction with bids cannot be treated like an unbid listing.
At the end of a session, distinguish completed sales from active listings and unsold inventory. A tidy companion inventory helps you see what you own and what is reserved, without confusing those states with the gear in your ARPG stash.