Strategy for popularity events

So I typically do not do very well these events and would love to have a discussion on effective strategies for these types of events. What I typically do is only help one type to (with exception to the fourth that adds a love bonus to everyone) to avoid working against myself. And when they ask for an item after a quest I try to maximize the gift for the biggest bonus. When else could I be doing to help myself try to unlock a happy ending and win one of these cards?

Well, there's not much beyond that to help. One thing that could be done, though, is getting the early rewards on each princess before focusing on one. That way you'll have a lot more resources to use if you're focusing on your favorite girl.

From what i've heard, *5 EU is required for casually get a 6* girl, though i haven't participated in one seriously for quite some time now.

I have done some of the popularity event and this is how I have done them (free player):
The last popularity event I tried to get the 7* total reward. I missed the first day but since the eu 6 was really cheap (<15te) I gave it a try. I did all the fights and gave candy when I found the girl that gives + to all (while in stud mode). It took me only 40 pots to get the total bt 7*.
I also tried to rank in an other popularity and that went a little bit different:
1st day I used no pots and had no event unit.
Second day I bought an eu 6* for 100 te.
Last day my ranking was really good so then I saw that mao ranking was the best for me and used all the stud mode on mao and ignored the others.
That time I burned 450 pots but I got 2 ranking 7* and one bt 7*.

I am a free player too, thanks for the advice. So what exactly does the eu units do, give you bonus points for using them? Do you also receive points for using one of these units if your ally has one?

What to do in this event depends on what you're trying to accomplish. If you're going for the 4th girl then don't skip anyone. If you defend one princess you lose points on the other 2's individual rankings ONLY, your total love points increase the exact amount you get for defending the girl.

Save your pots and flowers to burn when you have time: borrow a good eu if you don't yet have one, give the 4th girl a flower, burns pots, only defend the 4th girl and skip everyone else, use all the beans you can, and don't lose. That strategy worked for me.

The only time I really played I had eu 6* for cheap so it was a breeze; eu as lead gives bonus points and higher chance to encounter the 4th girl so it's extremely useful. The only event where you benefit from eu allies is panel iirc, they're needed to beat the best boss. EUs this event are much more scarce (step up, and probably not many ppl are buying).

If you want to rank on individual ranking though, that's a lot harder. You probably need good eu for this. What I see ppl do, correct me if I'm wrong, is playing normally and defending everyone until either you get all the resources or you get the lp 7* then you give the girl with the most love points flowers and burn.