For me, I never look the highest return(ROI)on investment in gambling site. I'd rather choose reputed and legit gambling site, because for me if gambling site gives high ROI I think they are a shitty gambling site. But this is a case to case basis depending on the gambling site you're planning to invest.
I found this link thread offering to have crypto game investment.
https://bitcointalk.org/index.php?topic=2445163.0Sometimes looking a reputed and legit site is best when you want to invest, I'm sure there are some reputed site that has High ROI. It seems that you want to invest in gambling, try to read the sites review to be sure about the site your going to be get in touch with.