Items from different expansion

Hello, I am new and I have got one question that bothers me, but I can't find answer.
I have got Guild Wars Trilogy but no Eye of the North expansion. Can I buy and use weapons/armor that come from Eye of the North ?

Yup, you can. You just cannot venture there to get it yourself!!!

Most items (except dungeon rares) you can get in the normal game yourself, either from the FOW, UW, or Zaishen Chest

Yes, that's fine. You'll need to buy them since you won't be able to get them yourself. Keep in mind that armor is customised to whoever obtains it so you won't be able to get any EotN armors. Also keep in mind that EotN equipment isn't necessarily better, it's just a matter of different looks. Weapons and armor haven't been getting progressively better through the games. The best armor from Prophecies is functionally equivalent to the best armor from EotN (likewise for weapons). Unless you're looking for a particular weapon skin, you won't need to bother buying EotN weapons.

simple answer
weapons yes
armor no
hero armors can be bought, but not applied to your heros since you need to talk to an npc in eotn(but they can be bought and resold if that is your intention)
also anything customized already can't be used of course.