Oanda is a Forex broker that has been around for a very long time and there is not a minimum account size and there is not a minimum position to take. You can open an account with $10 and trade 5 units of a pair like EUR/USD. Per trade profits are calculated down to .0001 cents. So you can trade live and risk as little as you want 24/7.
Just a word and it is not really a negative, is Onada is what they call a bucket shop and they do not actually give you a market position, they just give you the position on paper and they fade you by absorbing your profit should you have one. You still realize the actual P&L in your account. Most traders lose so they make what you lose. For profitable traders with larger positions they probably hedge out when a position is taken or trade along with you for their own account.