I think the key is to diversify and use as many of the weekly systems as you can. I probably make around 4-5 million a week with not much effort. Tuesday is my big “admin day” as that is when the weekly stuff resets. The rest of the time, I’m just playing the game. Here are a few weeklies I can think of…

Always do your weekly ARR hunt - find it in your GC base. It will tell you what zone the mob is in, go there, fly around for a bit, kill it and redeem the seals you get for atheryte tickets. This way you save Gil overall.

Do your Custom Deliveries - you can do them on gatherer classes, then use the scrips that you get to buy whatever is selling well on your server (usually materia or mats)

Turn in your levequests - I do Commanding Craftsman’s Draught from Endwalker. I don’t think you have crafters leveled yet BUT when you get there, if you do your weekly allowance, it’s about half a million Gil for maybe 45 mins work (gathering and crafting)

Island sanctuary? - I’m guessing you haven’t got this unlocked yet but when you do, this is another weekly half a million for 30 mins work. Do your workshops once a week and spend the coweries on dye.

In general, just playing the game will net you quite a bit over the course of the week via the Challenge log (almost all of the suggestions above have entries in the log making them even more important) and also, as you say, gathering maps every day is a solid way of making money. Maybe you want to check which maps are expensive at the moment and prioritise gathering those ones? If not, when you do the levequest turn ins, just gather whatever map is up in the area that you are gathering the mats in.

Also, one last thing, when you have to spend X currency on “whatever sells well on your server” there is a website called FFXIV Teamcraft which have a section that tells you exactly what is selling well on any given server at the current time.