Im not sure if there is a minimum one needs to invest if pursuing that path. But i was thinking of sticking to my ZEC mine and drop 100$ into buying ETH every two weeks.
Yeah it is worth to invest,no matter of how much your are investing it will definitely will give profits but if you have more amount to invest then the chances of getting more profits are high.But remember that your investment need to be in long term if you really want to make profits.Every investments are worth in crypto currency but the coin we are picking is important if we want to make profits.
But I am not clear about your idea,are you going to invest $100 every two weeks in to ethereum?