I recently joined a new site since last week, called Bitvest. I put in my investment there, more than $150. It is a big amount for me,,, but I had been collecting some bonuses recently from the end of 2018 and decided I will invest the extra in BTC. But different from my own personal holdings, I wanted to experiment by investing in a casino bankroll.
Many others as mentioned above, but I wanted a site with visibility:)
Im beginner.How much should I start? Im afraid that is scammers.
There are a lot of gambling sites which are a scammer and those sites who offer investment plan like a Ponzi is too much risk, we should avoid those types of Ponzi scammers.
if you are a beginner you should read bitcointalk forum more

there are many legit casinos that offer investment, simply google and read the corresponding topics
Ponzi scammers have nothing to do with the gambling sites, totally diffrent sites and totally different ways of earning money
investment is risky too , do not think of it as 100% risk free