I need help making gold coins cost real money, or watching ads. How would I do this on my multiplayer game?
You’ll want to use third party services for anything financial. AdinPlay is a very popular choice for browser games. In addition to regular ads, they have rewarded ads which allow users to watch a video ad for some kind of reward. XSolla is a commonly used platform for in game transactions (user pays real money for items, in-game currency, etc).
I’ve never used either of these services myself but I’ve seen tons of web games use them.
In addition to @Devortel’s great answer, I’d also recommend PlayFab. It supports XSolla payments as well as a huge host of other payment providers. Setting it up is very easy, and the documentation is great.
Okay, thanks! So I now I know some good services, but how would I set this up, I mean I want it fully functional.
A good place to start would be the documentation here - Items - PlayFab | Microsoft Docs.