For most wares, caravans aren't a good supplier, because even when ordering, you'll get at most four extra; four more bins of pig tail cloth won't make much of a difference.
Things are different when looking at stuff that converts into more goods or stuff with large variety within its types: ores and coal are good things to order: if the dwarfs offer all three types of iron ore and you order them at top priority, that's another 48 bars of iron per year. Four lumps of bituminous coal are good for another 32 or 36 coke. You can order very significant amounts of leather and cut gems, because the dozens or hundreds of sub-types are all counted separately. Ordering lots of leather is definitely useful, ordering tons of small gems is mainly good for blinging up your fortress. I regularly order two of each from an arbitrarily-picked two pages of gems and use them to encrust whatever ware i decide to hoard (crutches, e.g. - my volcano fort's pimp canes must be the stuff of legends).
But apart from exotic animals, leather and non-local ores, caravans are mainly good for hauling off garbage. You can impose challenges upon yourself like only trading with the elves, or making a bowdwarf squad or never producing booze locally (while keeping your drunks drunk), but a fort in a decent location can completely ignore trade without problems, up to building an utterly unreachable depot (walled off, on a pedestal with no access ramps...) just to avoid traders going insane and accidentally donating their wares.
Re: negative thoughts from atomsmashing - only when it was a masterwork. Clothes also disappear after a week or two on a refuse stockpile, without causing bad thoughts. My old clothes removal is simply a 1x1 garbage dump with a refuse pile painted underneath; no mechanisms, no risk of smashing a dwarf along with the rags, no hurt feelings. Refuse piles aren't so good to get rid of excess food, because currently, prepared food never _starts_ rotting when on a stockpile of any kind, including refuse. You have to dump it off a stockpile to get the rotting started.