Great writing
This piece here has excellent writing and composition behind it. I love the instrumentation you chose and I have very few complaints on the structure and progression of the song. I know you said you have no formal training (neither do I, haha), but it shows me that you understand theory and have either taught yourself a hell of a lot or have a unique ability haha. Anyways, excellent structure and movement of the piece. Great buildup and energy.
What's holding you back is the quality of the samples you're working with. I know how it is, though. Everyone's on a budget, especially these days. But god, to think what this would sound like performed or with some orchestral VSTs. I'd recommend saving up for something (I would recommend EastWest Symphonic Orchestra - if that's too much take a look at the Garriton Personal Orchestra). I know it's a big investment but you WILL NOT regret it.
Only suggestion I could give you is to take what you're learning with reverb and panning and take it further. Try running your reverb on each instrument (or set of instruments) through a bus or auxilary channel. Then you can take your panning for your instruments and set it up like an orchestra would sit (google orchestra seating chart if you don't know). Take your reverb of each channel and pan it opposite where the instrument would sit. Take a minute to consider what I'm saying here as well:
A reverb is the natural reflection of the environment a noise is played in (you most likely have figured that out haha). Anyways when a violin, for example, plays on the left side of the orchestra. Your ears here it positioned there but a few split-seconds later your ear hears the reflection off of the orchestra hall's right wall. You want to mimic that and make your instruments sound like their really being played in a real environment.
Aside from that. Try adding sample level (about 200ish samples) delay onto the instruments that would sit in the back of the hall. This will trick the ear into thinking that instruments are sitting behind others. It's not very noticeable until the final change, though.
Oh, I would also encourage you to switch up the second buildup. It sounded exactly the same as the first one. Granted, I'm nitpicking but hey, everyone likes opinions right?
Awesome piece though, I just wish I could help you out with better samples; you'd be in a whole different ball-field.
Nice Job, a big 5-age on the vote!
~SinJim
PS - The piano samples I use are from Logic Studio - Eventually I'll be purchasing professional quality samples, but I've also just purchased a microphone which means I can now record my real piano which, by chance, was just tuned Hoorah!
Sycross 
