The rapper, and apparent day trader, tells TMZ … Robinhood made a big mistake when it blocked customers from buying more stock in companies like GameStop, AMC and BlackBerry — and as a result, he’s having second thoughts about sticking with the service.

The way Ja sees it … Robinhood rigged the system against everyday folks who were taking on Wall Street’s establishment and winning, so it’s time for retail investors to take their trades elsewhere.

While Ja’s steaming about the Robinhood setback, he might want to take some stock advice from Jordan Belfort, who’s suggesting a different way for normies to win in the market.

As we reported … Robinhood says it will allow trading Friday for GameStop and all the other securities it blocked Thursday, but only for “limited buys” as it continues to monitor the situation.

But, listening to Ja go off, it sounds like Robinhood won’t be able to mend fences that easily.

Sounds like Ja fancies himself as a Wall Street wolf just like Jordan … and he’s got some ideas on how GameStop can cash in on the craze.