Don't confuse yourself because I only made use of a scenario where if you are being paid monthly salary of $1500 and when you removed your utility bills and other bills, you will have a left over of $200. You don't have to use the $200 ans invest in Bitcoin. You can always divided it into two and use half for investing and keep the remaining as an emergency fund. That is after you have removed all necessary bills including savings.
And that option is very smart The example you give is what happens in real life for many of us , If I have $200 left over , I also divide it up I can use $100 for the DCA method and easily buy my BTC, I'd have $100 left over, which I can divide up for miscellaneous expenses and always keep some money in my pocket, which is also necessary to resolve any new issues.
When buying BTC, the idea is to do it right The money you buy doesn't have to be withdrawn again because it simply wasn't calculated correctly and you need that invested money The method won't work, and you'll become financially Undisciplined.
I can't agree with one thing you said to keep a part of your discretionary income for buying in the DIP so that when the price of Bitcoin decreases in the future, you can use that opportunity. But if the price of Bitcoin does not decrease in the future, then you will have to buy Bitcoin at a higher price with the money you did not invest. This will miss a good opportunity. So I personally think that investing some portion of your money in Bitcoin on a regular basis is a good idea, without paying so much attention to the fluctuations in the price of Bitcoin.
That's a great idea to leave some discretionary income to be able to buy the dips, but it would be ideal if while leaving a part to buy the dip, you continue the plan of buying with the DCA method, that is, if you buy BTC weekly, then continue applying it, and another part to buy those dips, it's always good to do it that way and it's a phenomenal idea.
By investing using this DCA strategy, you can invest regularly in small weekly or monthly amounts and these small steps of yours can bring you something big at a time. You can invest the remaining money in Bitcoin from the income you have and use it for your necessary purposes. However, you should refrain from spending your money on unnecessary things. Always be one step ahead for the future and be aware because if you wait for Bitcoin to dump, you may fall behind because you will be disappointed when you see the price of Bitcoin increase. In that case, the DCA strategy is the best for you.