Before I moved on from Atelier Elie, I wanted to get what might be called the “best” ending, where she and Marlone become “true” alchemists. In my first post on the game I outlined the way to get this ending.
These “marie point” events are not easy to activate. Even on my replay, knowing what the events were, I was stuck at 7 points for a while because I couldn’t get the necessary things to happen.

What I eventually figured out is that the event with Mirukasse requires your friendship to be above a certain point. Normally when you pray at the church nothing happens, but if you go on a day ending in 5 she will ask for a donation and that increases the friendship. I did this a few times and the event finally happened where she asked me what my goal/dream was. This is confusing because I was pretty sure this event happened on my first playthrough but because my alchemy level wasn’t high enough, I didn’t have the option to respond in the correct way. But given what happened in this playthrough it seems unlikely my friendship with her was high enough to activate that event so early in the game — perhaps I was misremembering some other question that she asked.
In any case, once you have the necessary points you just have to get Marlone’s friendship up to 70 — I’m not exactly sure how the friendship works, but if you just keep going out to gather items you will eventually get there. I think you can just go to the nearby forest and immediately leave, and just repeat until it’s 70.

Finally, you need to raise Alchemy level to 40, go do an event in the far away city where you first get Marlone, and then raise Alchemy level to 45.
I am not certain exactly what the most efficient way to get alchemy levels is; I don’t know if you get more experience for more complicated items, or what. I did eventually hit on a method that raised the level pretty quickly.

Basically I spent a month or so crafting new items (or working towards that goal). I had 5 fairies that were all collecting items from the far away places. After that, I would go to the tavern.

You get experience from doing requests, so I would do as many of the “rich” requests as I could — even if I had to do them with cheaper items that lowered my popularity, I was always able to recover that through doing the regular requests or having at least 1 or 2 of the rich requests go well.
After that I would often take one of the bar requests, fulfill that, and then craft more items until the month was over. With this method I was able to reach level 45 fairly quickly.

The ending is fairly short; Ingrid is satisfied that both Marlone and Elie have discovered the true meaning of alchemy, and they each go on their separate ways to continue to perfect their craft.
At this point I felt like I had gotten enough out of this game. It’s fun, but the system is still primitive enough that it starts to feel tedious and limited after a while. I could have gotten the other 5 or so endings, or tried to fill out my item book (it’s at 183 out of 200 items), or tried to go for some of the “love” related events. But in the end the game is just a bit too formulaic to play it that much.
The next Atelier games are ports of Marie and Elie to the Game Boy in 2000; from what I understand these are not just ports/remakes but semi new games. I probably won’t play them much but I will see what they’re like. The actual third Atelier game is Lilie, which came out for the PS2 in 2001.