Thanks, I'm gonna update it when times comes but right now Yuumi style may be very drastically affected by her "mini rework" in last patch, so I can't really go in detail about what's the best way for him, but I can say for sure she's much weaker early, so until you finish your first item and put some points in Zoomies you should just farm money with her Q, and when passive is up with a basic attack or two if the situation allows it and you will not get hurt.

Depend of game, if you are ahead you can go full ap, I'm pretty sure I explained what items to build for what, or at least the important ones that are not so intuitive.
Glacial build is litereally for glacial runes, I'm sorry if you can't figure that much, dark harvest for a full ap build or mostly ap, not recommanded right now tho since Yuumi poke got drastically reduces over last patchs.
Aery is the standard one and useful in any situation if you want "flexibility" but glacial and harvest have their own niche that aery can't provide.
Font of life can br proc by your main skill and the one you probably would use the most PROWLING PROJECTILE (your Q), shield bash is a **** rune for Yuumi tho, why would you want to to waste more time and auto AFTER procing your passive, insead of attach back and poke them with something that actually do some damage and in same time nullify some damage that your adc would take? bone plating is not a rune for Yuumi either, especially right now that Riot push Yuumi to stay attached more than usual.
I'm not sure how much do you love to stay deattached but if you want to proc everything you just mention you would be probably dead right when or before casting you and me.

Anyway if you are really indecise what build to adopt just take the first one, and depending of your situation you may build an rabadon/morello insead of kinghit's vow.

btw better double check skills stats, I was to lazy to update them everytime a nerf change got place. (but if I look choose, i can clearly see you barely looked into build without reading anything else and just claim i did not explained, since you assume font of life can be proc only by ult when its clearly mentioned in guide that it's proc by Q)

From what I seen so far they should work perfectly normal, but I didn't get the chance to test it in a clean space such as a custom game with some other 2 guys (mainly cause people don't really want to do it), and in practice tool bots are to afraid to attack the dummies.