Cables are easy in 2.93 version of blender.

Inspiration

Beginner

This is great.  Cables seem very easy now in blender. Oct 2021a

How to make Crystals

Inspiration

If you take a little bit from each tutorial, like the driver part from the first one, the texture the intermediate one, and the volume absorbtion from the last one.  You should have a very good looking crystal.

Beginner

Chris has put out quite a few tutorials that are easy to follow.  

This is a tutorial from 2.7, but the ideas should work with shaders in 2.9.  Very nice style

Inspiration

ArtStation - Ansel Hsiao This guy is an excellent modeler.  His Spaceships are movie quality.

Get the models

Sketchfab

TurboSquid

Blendswap

cgtrader (has the best, most detailed models.)

Inspiration

This is one of the best Star wars shorts I've seen in terms of quality.  His laser blasts are excellent, (Has a better glow and blast object than the below videos) and the shows what the Unreal Quixel Mega scans can do.  He could've used Iclone7 to make his character, but used a Human Generator which ;also makes shape keys for facial poses. Just fantastic.

First some inspiration:

Here is a nice warp sequence

Beginner

Make 2d Nebula you can put in your backgrounds.

This uses different textures nodes for a different type of Nebula