1. What does it mean "I collected unemployment"?
It means you received financial benefits from the government after having lost your job.
2. What does it mean "More companies are now bringing them on as permanent employees"? I think it means that they are hiring people as permanent workers, but isn't 'bring on' a slang meaning "show me what you've got"?
To "bring on" is a BrE expression for hire. More recently in AmE, "bring it on" has appeared as a slang expression for "I'm ready for a conflict with you" or as you nicely put it "show me what you got". "You've" is a little too correct for this aggressive slang phrase.