I have been exploring portfolio trading myself for a couple of weeks now. From what I have gathered you need to diversify on as many instruments as possible, with as many strategies as possible. The less correlated the result equity curve per system is, the better your drawdowns will be and the smoother your equity curve will grow. When you begin to look deeper into portfolio trading, the positives are a lot and the one negative that stands out is how much money you will need to start trading. The more the strategies and instruments, the higher the capital required, mostly.