It's my third month being serious on Upwork, got Top-Rated status, and on the way to the first 10k.
Be consistent and suck it up at first, then it'll be downhill.
It's been more than a month since I sent the last proposal and I'm fully booked until August.
People will start inviting you.
Sending lots of proposals will make the algorithm showing you more often.
My guess is they want really active freelancers to get jobs asap (so they can earn as well), that's why sending a lot of good proposals kind of cracks the algorithm.
Spending $15 on the premium account is good IMHO, you get 80 connects, can see the avg price bid, and, most important, hide your current earnings.
Another thing is starting to aim higher immediately, starting from small jobs is a great strategy but after a couple, it's time to scale.