Trading in altcoins can be started even at 0.001btc but that kind of trading doesnt worth any think,the minimum amount i say should be 0.25btc reserved for that.Its not neccessary to use them all at once,must that much must be in reserve.
I think even 0.1 btc would be sufficient.In fact there is no minimum amount needed for trading but if you want to make big,invest big but you should be able to afford the risk also0.25 is actually just too much for a newcomers to trading job,0.001 is quite effective if you can manage to always making profit and the fees doesn't matter at this time,otherwise still better to save money and gain more to start with higher balance but there's nothing wrong to start with 0.001
you can not expect anything if you start trading with 0.001 lol ,
even 0.25 for most trader are still very little capital ,
you need to take a risk even you are a newcomer it is the important thing in trading.
i am start trading with 0.001 and i only buy altcoin with small price in under 50 satoshi and suddenly i have my luck that altcoin is getting jump for the price until reach about 200-300 satoshi and i can make much of bitcoin for that. so don't under estimated if 0.001 can make much of bitcoin
i do that too, start trading at 0.001 (small investment especially on ICO at yobit or if I happen to see a pump on a coin happening) then mostly i buy those at 1 sat LOL. It is a gamble in my part because of the very big chance of that coin becoming worthless. Well at least with that amount im not bagholding huge number of coins. Then if 50% profit is seen i sold all of it then buy at the same price with the profit and keeping my initial investment safe.