If you are trading on margin and are losing money, you would probably also be losing money not trading on margin. So you need to look at how you trade. That being said, I would say don't trade on margin until you can break even for at least 6 months, before you even start thinking about it again.
Statistical edge is only applicable if one is assuming an underlying pricing model, like Black Scholes. But even that is recently being questioned as being valid.
I think it's ok to jump from strategy to strategy as long as you play with a limited amount of risk capital. After all, actually doing is the best way to learn. Sometime I will set up separate tabbed pages in IB TWS and trade a small number of contracts to test out some strategies...
In defense of Metastock:
I actually find Metastock being somewhat limited as an advantage. If you system test over a long (as in 15 years or longer) period of time, most of your successful systems will tend to be on the less complex side, unless you want to curve fit.
Except if you day...
I can see Forex for intraday trading when you will not hold your position overnight.
However, For longer trend trading you also need to consider the overnight interest fees on Forex, which can take away any cost advantage.