Welcome to NG.
I found your piece rather interesting... it presented a solid chord progression (you write chords before melodies, yes?). I find it more a melancholy piece in general, it's not particularly scary or spooky, simply dark and rhythmically interesting (although yes, Johnfn is right- you should try to use your melodies more effectively- for instance, you often throw in a brand new melody/motif and one thinks the song is going to go somewhere different and it returns instantly to the original progression).
It reminds me of more contemporary compositions with a lot of repetition and arpeggios and such. I enjoyed the overall tone, but it never reached an effective climax in my opinion. What you need is more deep strings, fuller chords (be it through woodwinds or middle strings), and a solid melody we can identify ASIDE from the chord progression. Also consider voice doubling, or having multiple instruments play a part together in unison or octaves.
You certainly have some good ideas for your orchestration, you just need to pick up the rest of the orchestra here and try out some different instruments than strings and percussive strings. Many composers now favor strings over other groups, but I find woodwinds and brass can present feels that strings cannot, and also play as dark or as soft as any string section.
If you want to go into more scary music, you'll need to practice writing darker music, almost to the point where it is ambiance- very deep strings, chaotic off-beat hits, all sorts of percussive nonsense (hehe). You'll also need to use more brass. The structure of scary music is complex- sometimes it is very very open with full octaves and such, symbolizing the unknown and a lack of comfort; sometimes it is very very close with intervals of 2nds and minor 2nds and all sorts of odd chords, symbolizing closeness and a confined feeling.
Try experimenting with chord patterns that evolve into different patterns too so you can add elements of motion to your songs, and then try bringing in more parts! The worst you can do is learn something and have to start a new project... I have dozens upon dozens of works-in-progress just sitting in my compositions folder that I never finished because I was hit with a neat idea while working on them.
You should also look into your mixing/mastering a bit more, so instruments that bear elements of the melody don't get buried under others that don't.
I can't wait to see more work, you have a promising style. :)
Keep compos(ed/ing)!
-Samulis