It must be mandatory for all of us to develop habit of savings. Their are lot of ways in which we can do savings and best of it is to invest in Bitcoin. Everyone has it's own limitations for investing in Bitcoin, the one who can easily afford 100$ a week should invest 100$ per week while the one who can afford to invest 10$ per week must keep investing that much money. It may look boring or useless in start but it's real benefit will be evident if you keep investing for years. Bitcoin price will go up with time and we must be ready to take advantage of that price hike by investing at right moment.
Bitcoin investment shouldn't be done the way you have just explained it, when you invest all you get in a week into Bitcoin investment it can be considered as gambling because you are not investing from your discretionary income, if you invest all you get in a week into Bitcoin what will you then use to sort out your daily needs or other necessary needs when they come up.
Since bitcoin investment is for a longer time we are expected to invest using our discretionary income.
WatChe was right but he has some off point from what he was saying regarding mandatory because is like forcing someone to have a savings and secondly I don't no what the savings should do for the person who is investing on Bitcoin, weather they will save it for other things or they will save it for the same Bitcoin purposes. However on the last part @WatChe is not far from the investment ethics because he was implying that if $100 will be good for you take it for all the time of investing or if also an amount that is lower is rather perfect for you is not bad, of course that's how everybody invest, even with all the strategy a comfortable amount of investment is a thing that should not be disregarded because is important.