Marketing Quandry

Hello All. I'm new to self-publishing, with one book out. I've tried my hand at marketing and promotion, but it's a heavy slog (as it's well beyond my skillset). I have connected with a couple of marketers and it's hard to tell if they're a scam, legit or what deal is better than another. If you have advice on how to sort through these things, I'd appreciate it. Thanks.