What air purifier would you recommend?

I don't think air "purifiers" are worth the up front cost or the cost of operation. I put a better type of filter on my furnace and now have no dust.

I realize you are in an apartment, but you might consider paying a furnace man to put one of the 4 inch filter boxes in the cold air return if there is any way to get to it, probably at no worse cost than the "purifier." Failing that, just get the better 1 inch filters and change them monthly.

Do you have a humidifier? The best ones are attached to the furnace, but in an apartment you might have to shop for one you put water in yourself. The biggest ones do make air more breathable.

Another way to remove dust is to occasionally dust the ceilings and walls. I have a big, flat hard floor mop that collects dust nicely.