It's called the coin game, basically you use a coin to choose if you go long or short then manage the transactions (cut losers, let winners run), you may make money over time. Also you can run simulations on MT4, basically you randomly decide a time and put limit orders below the price, you can optimize the MM parameters to make the system profitable.
By no means does this produce the most profitable system ever, but it makes the point that MM does have a major impact on system profit.
There are different things which can swing the odds in your favor (support, resistance, trend), but those things are normally tough to automate in addition to a human can pick it, I focus on automated systems mainly, simply to clarify my remarks.