Check out the risk before you try something, especially with money. Your 50,000 demo account is far too small for 3 lots and margin 500. These settings will likely wipe out your account before you can make any profit.

Ok, it's only a demo account, but I suppose you want to simulate how it feels to trade with money? If you really want to risk all your 50,000, leave the margin at 50 and set the lots to 4 or 5. Then you can win a lot, but also lose a lot. With the original settings of 1 lot, you only risk about 10,000.