There are plenty of videos online to help you with that, especially the more popular aesthetics you listed.

Dark Academia:

https://m.youtube.com/watch?v=D4vVp_FK1jE

https://m.youtube.com/watch?v=tTmCxVsagRw

Grunge:

https://m.youtube.com/watch?v=vdwlDLdS67k

https://m.youtube.com/watch?v=1L5N_4_DTa4

E-Girl:

Vintage:

https://m.youtube.com/watch?v=uzj7GWiW-PQ

https://m.youtube.com/watch?v=xSOC6vkyeaA

Spacecore:

The photo for the Spacecore aesthetic may not match the wiki aesthetic we have here. The wiki aesthetic has dark blues and things that remind someone of the night sky. But I just want to help, pls don't take this offensively @Alldacolors !

Why would I take offense, Anika? Thanks for telling me! Perhaps I will find a bedroom or something based of your description.

It's just hard to communicate ideas on here without having someone get mad. Thanks for your response! :)

Here, for the original poster, a bedroom based off of this wiki’s definition of space core.

The blending part may be difficult, and as a person with multiple aesthetics and a room that looks cool (at least imo) here's what I did:

1. Pick a set main color and a set accent color- this is for furniture and metal things like lamps. The two colors should be consistent for the whole room. For example, for mine, I have white and gold. For yours, black and silver are strong contenders. If your furniture didn't work out like that, do what I did and DIY it via spray paint.

2. I decorated in a way that the two walls with my decorations are different, but still cohesive. I did this through having a color palette with two or three colors that match. For example, one gallery wall is black, dark blue, parchment-paper, gold, and white. The second gallery wall has the last three colors and pink and light blue instead of black and dark.

3. Collect what makes you happy! I personally collect postcards from places I visit, clothing tags that look cool, DIY'ed art, and even knickknacks like organza pouches. Simply being able to look at things and recognize their attraction is enough.

Check out the Blending Aesthetics page for some info too! I guess my question is, are you applying dark academia to an egirl aesthetic, or egirl look to dark academia?

That's a great guide! You know, I'm an aspiring set/interior designer, so this is very fun to think about.