AlexeeSan9

Hello! Haha, thanks for welcoming me to DA. Be prepared for a long reply. I'm not very concise. And I wanted to fully respond to your comment.  
Your observations are greatly appreciated! It helps to get feedback from a fellow artist rather than either myself - who can become self-critical easily - or friends who don't draw/paint/etc, who see mainly the good points in the artwork. Either extreme isn't really constructive criticism, so to reiterate: your objective observations help me to see not only what I'm doing well, but more importantly what I need to improve on/practice.
What you mentioned about how my advancement in tone and colour possibly going against me later on hits the nail on the head. I vaguely realized (in the back of my mind mainly) that although utilizing those elements in my artwork gave me a head-start and, yes, also made me feel like I was accomplishing something, I didn't really understand the mechanics of those elements or how to analyze them further, and to ultimately project that onto my art and thus elevate my artwork. You explained that pretty concisely. Makes a person realize that talent is great and all, but it can truly burgeon into something greater when combined with the assets of skill, practice, and well-rounded knowledge of the different elements of art.  
Thanks for the tips for practice as well! I'm taking my first drawing class this semester, and just that has helped me with perspective, contour lines, thinking about complex forms as an aggregate of simpler forms, etc., but it's also nice to hear from another artist who sees my art on DeviantArt that represents my own style and also shows the consistent flaws/room-for-improvements in my artwork. I started my DeviantArt a few months before I took the art class, so the pieces/sketches/etc on here can show what I was doing in my artwork before I started considering the basic elements of art that can be used to an artist's advantage. 
Also, thank you for the compliment! My art journey thus far - especially in the past two-ish years that I've been drawing almost everyday and got more serious about it - has been a fulfilling, fun, sometimes frustrating, but overall great experience. I used to be more self-critical than I inherently am (I think it's pretty normal for creative people, and people in general, to be self-critical), but I've come to embrace the infinite room that there is for improvement, experimentation, failure, success, and growth in the journey of creating art. There's actually a poster in my math teacher's classroom that has a diagram of what "success" is believed to be, and what it actually is. The former was a straight, impeccable line that went from "Point A" to "Point B". Conversely, the latter was a squiggly, crazy line that clumsily meandered from "Point A" to "Point B", but briefly tapered into a straight line right before it reached Point B. 
Anyway (lol I tangent a lot - your comment has evoked a lot of thoughts about art ^^), the fact that you took the time to comment is awesome. Your perspective is very refreshing and thoughtful!