You can get up to 7 ampule of one type on the world exploration and 6 exploration per day. With enough luck it's almost one set of each ampule per week. With all the others source of ampule, it's easy to get them. Same for gold. It's 150k free each day plus all the other incomes. I'm pretty sure you can get them back before your next 6* (onay mabe not if you're doing the 30FG gacha).
At the begining, it's hard because you have a lot of girls/equipmement/memories to level up. But soon the amount of things to level up will decrease and gold will increase (more stamina, more missions, more gold). Same for ampules. You got way more ampule that rainbows (unless you're super lucky or you're whaleing).

Back in the good old days, there was a lot of daily missions. Some of them where "gives level up stuff 4 to girls 4 times", "gives 4 gifts", "roll the regular 2*~4* gacha 10 times", etc. It's gone a long time ago but I still stick (somehow) to this. I limit my gifts/level up/ect each day, unless I'm aiming a precise rainbow for example. It take more time to build girls but it help a lot to save ressources. With years of this I'm now swiming in gold/leveling spirits/ampules/gifts/ect.