There is no solution which is 100% perfect to stop the spammers misusing the gambling chat.
There are certain solutions that can actually restrict spanners to a huge extent, but that would require setting intense restrictions which could possibly drive away legit gamblers thanks to the strict rules which is why casinos think twice before implementing these rules.
The easiest one to implement is that temporary ban the user on chat who asking for money or spamming links after X no of times.
I have seen such rules in the trading exchanges platforms and it works perfectly to stop the spams.
It has been implemented since long time ago by Stake, seems that you are not an active player here. Stake has many chat moderators as well as a BotMod to minimize the spam. I believe there many accounts are banned (temporary) since the first day of Stake till this time. We cant deny the fact that spam does exist on almost all gambling site's chat, especially gambling site that has so many users like Stake.