Going to play on a newly established gambling site we are not necessarily at higher risk than when we play on an old and well-known one. What we must do before registering on a site is to check for reviews and other info. The new site can be opened, for example, by a known and respectable owner of other site, and if that is the case, you are not risking much, registering in this site.
Reviews can be very helpful in making a decision to gamble on any newly created site, but don't trust them much. In such cases, I usually trust only people whose reputation I know well and respect. Well, of course, you need to use small amounts for a deposit, do not transfer large amounts to where they can disappear completely.
You are right, some reviews are paid, positive and even negative ones too. What we should do, is to search for the info on different sites, independent from one another. It's easy when you are dealing with an old and established site, but for the new ones it's harder. This forum helps a lot in such case. It's enough for me to see just one positive review from a member I trust, to not be afraid to play on a newly appeared site. And there are hundreds of such members on this forum.