yes you can surely start trading from 0.5 Bitcoin and i do not think that 0.5 bitcoin is less amount for to start trading and i am sure you can get a maximum profit through trading by 0.5 Bitcoin .
to start trading, it is not about the profit in the beginning but instead it is more about keeping the risks as small as possible while learning how to trade. and that takes time and some wasted money to make the mistakes and lose some money first because of making a bad trade, or trusting a scam ponzi scheme altcoin. but after that you become more confident and you can invest more and think about profit then.