Amateur needs mix critique and advice on reverb

Working on my solo project Mechanevil and I got what I thought was a mix that was about 80% of where I wanted it to be. Hoping when I add vocals, it will fill up the sound.

That said, I am an amateur when it comes to mixing. What should I have done differently on this?

https://soundcloud.com/jimmy-rage/judgment-mix-test-4

Also, one more question: How exactly would you have applied reverb on a track like this? There's no reverb on anything, not even drums, and I feel that's about 5-10% of the glue I need. I'm just so damn worried it'll sound like I recorded in a cave because I have a really small setup and can't spend too much on treatment as it's a rented pad.

Any advice you can proffer would be appreciated!

EDIT: Have updated the mix track.

From what I'm hearing you need to EQ the tracks. There is some low rumbling that needs to be EQ'ed out of some instrument, hard to tell, sounds like its coming from the guitars, and possibly the bass too.

All in all, it's not a bad start, I've heard way worse from amateur mixes.

Look up "Nail the Mix" videos on youtube
https://www.youtube.com/watch?v=2hplhOnwmUk
https://www.youtube.com/watch?v=9Xte6sUXjn0

Thank you for the inputs, I appreciate it.
I have a fear it's my room that's playing tricks on me, I'm high passing all the instruments except the drums to what I think is an appropriate level well above the space occupied by the kick. I'll try being more aggressive.
There's also the synthesizer occupying tonnes of low end, I think that may be what you're hearing. I really haven't figure out how to squeeze that into a metal mix. Cut too much out from the low or even the high end and I feel like the tone suffers.
I've seen quite a few of the Mail the Mix videos. They're really good! The course also sounds wonderful, I'll see if I can invest.
At the same time, maybe that money would first be better spent on some kind of rockwool panels or something. Absolutely no treatment in my room, so there are all kinds of resonances and reflections that confuse me. I fear that if the room isn't working, all the tutorials in the world would just be a waste.
My not-so-secret weapon has always been Mixing Secrets by Mike Senior in that regard!