I made the mistake of this being my first experience with re:zero and its characters. I watched it together as a friend cause I don't really mind spoilers. Luckily there weren't many spoilers, not that I'd remember them anyway from this unforgettable movie. I am sure the actual show is good, but I recommend staying away from this.
Do not watch this unless you're already a an avid watcher of the show and just want some mind-numbing fanservice that feels more like bad shoujo than anything. There is nothing you will gain from watching this movie other than fan service. You should fully be aware and have no further expectations.
It's just bad.