Investment sites is pretty safe, why I said this? Because this is a business model
Actually there is no safe in investment even in trading there is an involved risk. Any gambling websites that offers here involved risk so there is no safe. I just thought that it is not recommended to invest in a gambling website.
There is a safe investment but those aren't related to gambling nor casino. An investment that's related to casino is no safe but in the long run you can still make profit on it.
It's up to you if you don't want to recommend investing in casinos but it's not all about betting, they have an option to invest in their bankrolls. Few casinos are still doing this.