Is it necessary? No.

But I'd recommend it. Many of the topics from Lilies are back in Magnolia, including a character too.

You'll still likely be able to put most of the story together regardless but I think that having played the first beforehand might help you get a better grasp of it.

Plus it's a great game :D

I would say no, not much.
Each game is a separate story of its state related to the events of Blight and Ancients. We can say that each game is a separate puzzle of the overall picture, and on the one hand, it doesn't matter which one to start assembling. On the other hand, the second part contains references to the first part. You won't see it without going through the first one, so most likely after you go through Ender Lillies, you'll need to go back and replay the second part, if you're interested in the little lore details, of course.

Not necessary, but there are several references to the first game (Ender Lilies) in Ender Magnolia so you'd be missing out on some story bits but that's about it.

Lilies is an overall better game so unless you really hate the map there is no reason to play this first

no reason not to play lilies first

It would be kinda weird to not play lilies first, you would be VERY lost at the beginning but yeah it's playable, but i don't recommend to do so.