When the time i start trading i invested a 1000$ for learning purpose this value is a good start, but think the other factor like the fees or what site do you want to start trading there are exchange site that has a small fee but lots of them will kill you in a high fee. But i feel you can start with what you can afford.
In ny experience, even though I don't have money, I still work on Bitcoin; because money is not required before you get into forum, you just need look and join in campaign.