Not to late, just start small and get to know the sites you invest in.
I saw one thread and op was investing 1 btc each on these top betting casinos betking, safedice, crypto-games, satoshi dice and another popular site I forgot the name. He was posting updates weekly and currently it's on week 7. Safedice, Crypto-Games and Betking are currently at least 15% gains while the other 2 are less or some losses. So maybe you can start with those 3 top investing casino sites.
I personally never have seen someone talking about these casino bankroll earnings, though i have heard it from a lot of people that investing in a bankroll of a well-running and popular casino would be profitable. Can you provide the link of the thread you are talking about? I'm interested in this.
I think he means this site http://bitcoingamblingreviews.com/bitcoin-gambling-investments-112/