Items that give bonuses like +health, + %health, increased armor, increased armor absorption, and resistances. As well as OA and DA bonuses, chance to avoid attacks, and + % to all damage along others that I forgot to mention.
For vendor items, I am only talking about weapons, armor, and jewelry.
I would say it depends on what the character needs. Some prefixes and suffixes may be shit on a Death Knight with Krieg set, but if you take another set, the shit suffixes and prefixes may be good and the good may be shit, because they don’t provide stats you need.
Overall, Stonehide and of Kings are the only ones I remember being good for everyone, also of the Dranghoul is solidly offensive.
I pick up everything that says “Stalwart” or “Aggressive” as prefix (my RNG decreed that the former is way more common than latter); “Of Attack”, “Of Protection” or “of Readiness” as suffix. I also pick up everything that says “Stanching”, “Purging”, “Warding”, “Ordered”, “Resistant” or “Prismatic”. For Bosses’ MIs, I ofc pick up everything.
I don’t bother with rare version of these affixes because I primarily use MIs or crafted items to shore up resistances, so that I can go bonkers in other slots.