One of the big bottlenecks here is access to the low latency network connections & data streams. Successful HFT systems integrate information from ultra low latency news wires, trading activity in microsecond timescales, and are constantly testing things like dark pools for private market pricing information which isn't publicly accessible. Even if you'd written the ultimate trading app, you still wouldn't have that kind of access -- which takes millions in infrastructure and business partnerships you don't have, and no consumer brokerage would give away practically no matter how much you wanted to pay for it -- making the game unwinnable for anyone but institutions and highly specialized proprietary trading firms.