I'll tell you so that the minimum is not less than $ 100 . I know people who $ 100 did for the month of $ 2000 .But this exception, the optimal amount of input 5000-10000 thousand dollars .If you still want to see a profit!
I do not agree with you about how much the minimum money is. This could be 100 or 100k. It depend on your skill which you can do in the market. Also, there is nothing more things you can do when the prices are red.
But the benefited strategy you can follow in red market is to proceed for further coins as to get in large number so that a collection of more coins will give you maximum profit. If it is the Bitcoin then you are floating on the top and if it is other than Bitcoin then you are on medium altitude. All you need to do in red market is to buy more in number so that you may not waste your time.