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.
even with 0.001 bitcoin you can make a good profit out of it if you can manage to always get profit,it's indeed will be cut off by the fees but only small percents so it's not going to be a problem,it's worth trying to be honest
Certain exchanges indeed allow you to buy and sell with amounts as low as 0.001BTC, but this is an amount only used by people that are either new to trading, or people that put it into what seems to be a dead altcoin in the hope that it explodes in value.
You can have some decent luck a few times, but you can't constantly depend on luck when you try to multiply such a low amount. It's a waste of time and effort.
For a starter its better to start for that amount so they can experience the real tradings on there barehands and so if they lose they will not get hurt so badly since the amount they are risking for their practice mode is little enough that they might not notice,
But i'd really agree for your thoughs about having an high capital is a must since we totally earn huge profits for having a high capital in tradings.