You can trade with the lowest possible balance in your Meta Trader Account, however trading with low balance amounts will limit you in the choice of which pairs/instruments you could trade with because some have higher contract sizes or lower leverages. 

Indices and commodities have lower leverage so you would need more funds to open a position. 

If the selected leverage on your Meta Trader account is 500, you could buy 0,01 lots of EURUSD at 1.14682. That trade would cost $2.30 to open. IF you did the same with a leverage of 1:100, it would cost $11.49.