In simple words, if someone wants to invest for a long term or buy in dip and hold, then the total income must be divided into 3 parts. 50% daily expenses + bills and 20% Emergency & Reserve fund, that is, first complete the emergency, then create a reserve and the remaining 30% can be invested and this is the safest long-term investment plan. Now if you want, set up a DCA strategy with your profile for dip buying or long-term holding. If you keep it like this, it will be clear which money is for survival, which is as a buffer and which is for real investment. There are also many other strategies for investment, but this is the one I like the most and I consider it the safest.
Will 50% of your money be enough to meet your daily needs? Or is 50% of your total income a prudent money? Are you sure that this calculation will be applicable to everyone?
You have a misconception that investment is planned from the source of income. Investment planning should be based on your prudent money. My simple solution is that you do not have to do such a complicated calculation. After getting your salary, keep spending to meet your daily needs and continue this till you get your next salary. When you get your next month's salary, separate the remaining money from the previous month's salary which is prudent money.
Now you have to arrange investment related plans from this prudent money such as investment fund, backup fund and floating fund. Here I will not assign you any portion because every person may have different plans depending on their position. You have to consider how much portion in any fund is good for you.