To keep from putting off clients, especially new clients, one thing Upwork does is allow them to post their jobs without having to verify their payment methods first.
I have found good clients whose initial post included the notification that their payment method was not yet verified by Upwork. I apply to their jobs and make it clear in my initial proposal / cover letter that I can start work for them "...as soon as your payment method is verified by Upwork."
Good clients will understand that you expect to be paid. The scammers will move on to the next victim who doesn't fully understand how Upwork works.
There are lots of good reasons to avoid wasting your ever-more-costly connects on time wasters and outrigh scams, but I'd recommend you apply to jobs with unverified payment methods if the work interests you and your conversations with the client don't set off alarm bells. Just make it clear you won't start work until they've been verified by Upwork.
Unverified doesn't mean it's a scam. In fact, I've only had maybe two or three instances in my time here where an unverified client was trying to scam us. As long as you stress that you won't do free "sample work" or do anything outside of UpWork, you'll be good.
Also, avoid unverified postings that require bulk articles for low pay. Always demand what you're worth. If you're a bit more pricey, scammers won't even bother trying to recruit you and you won't agree to slave wages anyway.
Sorry you had so much trouble.