If I did the crazy costume project aka all the Christine costumes, in which order would you suggest to make the costumes?
I think it depends on your sewing level and of your budget.
I almost always recommend beginning with the dressing gown, as it's a less structured garment and a stable costume in terms of Christine's wardrobe. The large cloaks worn in the Rooftop and Mausoleum scenes is in the same vein.
The Hannibal Slavegirl costume and the Star Princess are good follow-ups, as they have corseted bodices with a lot of decorations (fun to work with) and KINDA easier skirts: ropes for the former, and layers of tulle for the latter. They also don't have sleeves, only decorative drapes. Seamstresses refers to "sleevils" for a reason...
The Elissa skirt is not super advanced in terms of shape and tailoring, but it takes tons of patience and time to just make and add all the decorations. Plus a giant budget when it comes to gold and gems... Could be a long-term project in between the others, so a good mid-way costume maybe? For the US version I spent a long time just custom-making the gold/red and gold/green tassels. The tabs and apron decorations was also hand-painted. I made this in between other projects, before I could mount it together.
The Serafimo/Maid costume demands a bit of tailoring for the breeches and the blouse/shirt, but if you find a suitable pattern they are fairly straight-forward in shape. Bonus: fun and frilly decorations, but not necessarily one killing your budget. My Serafimo blouse and skirt is a whole lotta trims, lace and roses, which in large came from my stash. So not the most expensive costume I've made, but definitely one of the frilliest!
The most structured ones are the Rooftop costume, the Wishing dress, the Aminta costume and the wedding dress. Obviously I started with these, which in hindsight was madness. Luckilly I didn't know... But here we're talking fitted bodices with sleeves, structured skirts with many details, and underpinnings. They also take a lot of materials, which means they need planning and careful material sourcing. For the Aminta costume I looked for the right salmon silk for AGES. I had already made the stomacher and netting petticoat, and I had the lace and trims ready.
These are only suggestions! As mentioned it really depends on your sewing lewel and budget. It could be smart to sit down and make an overview of what each costume will need, in fabrics and trims, in pre-bought decorations and self-made decorations, and in time. Gathering reference photos too. Sourcing materials is half the job, so you could start with that while making mockups for the bodices in plain cotton - for example.