Well, by now I have more than enough lvl 70 girls to fill a unit, so I'm at the stage where I can cherry pick the ones I really like or that really go well together.
As a result, leveling all the other girls has become something on the side instead of a necessity, and can I simply put all manyus of a color on the weakest girl I have from that color. So gradually, they all level up, including the 2* ones. Manyu maps are an extra, not a necessity.

Just when I get a new girl that I'd really want to put on my main unit, I put her on "priority leveling". All manyus of the appropriate color go to her, and I will generally run manyu maps to get more. Right now, I have Acacia, Snapdragon and Helenium on priority leveling, but yellow Manyus still go to whatever girl happens to be weakest.

Dragons I do the same as you: I try to have a stack in advance, so I get less pressure when a girl is about to evolve. At times, I've had as many as 12 purple Ancient Dragons on stock, simply because I had my default stock, and also completed some events rewarding dragons, while I simply didn't have any interesting purples to evolve.

Gold: it goes up and down. Especially when I level jewelry, it tends to run out quickly. But, when it's event jewelry, it's just soooo worth it, lol. I sadly ran out of jewelry slots now. I really hope they increase the max jewelry storage to something like 1,000 *soon*. 400 simply isn't enough to decorate all the girls.