Heyo! It usually takes longer until you find that first right client and get your first good review but after that, things will definitely improve. Just keep doing your best and never stop learning and improving your skills.
As for the shady client problem, that's why you should ask for advance payment. It helps you see who is willing to pay for your services and who will most likely cause trouble. Also, when required samples, never send anything that could actually be more useful to the potential client than getting a brief "taste" of how you work. If they try to convince you to do otherwise, you should avoid them. The only thing you're going to lose is the few moments it takes you to refuse them. 🙂