How do you tell the difference between a legitimate marketing effort and a scam? In show business, the difference can be surprisingly difficult to tell. There are a million pay to play sites out there, and they are not all equal. Some are very popular, like Voices and Voice123 that are, in my opinion, oddly set up and really expensive for what they are. However, if you know what you're doing, you can easily get your money back and then some. I'd consider Voices to be worthwhile, despite all of my gripes with the site. Beyond these, you can find sites that only book e-learning videos, or explainer videos, or animation, etc. These all seem to have some kind of price tag in exchange for adding you to their site. I find that these sites, more often than not, aren't really worth it. The "agent" doesn't really do anything for you other than add your demos to their site, which can increase SEO traffic theoretically, but is it really worth what they ask? Before you give anybody any money, look up their site and contact some of the talent on there to see if they're happy with the ROI. Personally, of all the sites I'm on, Voices is the only one I'm really alright with paying for. There are other sites that I've paid for that haven't so much as sent me a single audition. Then there are people out there claiming to be managers or coaches (or life coaches, or agents, or all of the above). They charge for a series of classes which usually involve paying for new headshots. They promise to put you in touch with agents in New York and LA. They use the word "contract" so often you start to forget what the word actually means. These businesses are scams run by con artists. I've found several of these in DC, and even started to work with one before suddenly having a moment of clarity, in which I had to forcibly take my money back via chargeback when they wouldn't give me my refund.
Here's a good rule of thumb: if somebody talks too much, they're probably lying to you. If they want money to represent you, they're not a real agent. Real agents take a percentage of jobs won through them; they don't bilk their talent under the pretense of maybe finding them work or worse, simply sticking them on a site and forgetting all about them.
Legitimate things to spend money on are:
Pay-to-Play sites with good reputations
Marketing and Advertising on various platforms (social media, Google, newspapers/letters, etc)
Business cards, postcards, URL domains, and other marketing materials
Acting classes and coaching sessions from verifiable sources with solid client testimonials (ALWAYS DO YOUR RESEARCH)
That's pretty much it. NEVER pay an agent to work for you. If a site wants $175 to put you on their ugly, outdated site, don't do it (I'm looking at you, locked-from-the-outside-with-no-real-phone-number Speakeasy). There are real agents out there who actually do their jobs, and they don't ask talent for money up front.
Another bit of advice: the telephone is your friend. Find voice actors in your area and call them. See what their experience is like. You'll be much more likely to secure solid leads to track rather than mining for gold on the internet. This is a tough enough business to hang with. Market yourself wisely, and you'll be ahead of most of the fledgling competition out there.