Welcome to the world of 3D! You are correct in that it’s kind of hard to give valuable feedback with just an image because we don’t know what you are going for with your model. What I mean is that this model might be perfect for a cartoonish theme, but quite out of place in a Battlestar Galactica theme - hopefully that makes sense.
Some things to think about: First, when you start a model, you might want to consider what it’s purpose is - is it realistic? Is it funny? Is it cartoony and non-threatening? Is it really big … or really small? Is it terrifying and mechanical … or peaceful and organic? etc, etc. If you have a “story” in mind for the object, it will drive a lot of the details and shapes you use.
Next, find reference that fits your story. If it’s “realistic” and you are creating a ship, find pictures of real-world ships and parts of ships. Do thumbnail sketches of overall shapes - get your sizes and proportions figured out before you do any detail work. Pick your favorite shape and model it very roughly and look at it from multiple angles to see if it still “reads” like you want it to - and adjust as necessary.
Next, begin refining your “big” shapes. Once you are happy with those, move on to medium shapes and then smaller details. Treat each as a part of the larger whole, but approach the modeling as components. When you see some of these amazing models, realize that the details are what make them stand out - but not just the details - but how the details are used to tell the “story” about the model. When I say approach the modeling as a component, what I mean is to not rush through your details. When you take on a larger, more complex model, you build it in pieces and think about it as “baby steps” to reach your goal. If you approach the model as a whole - all at once - you will get overwhelmed and are more likely to make quick modeling decisions based on expediency and not the strong visual elements that you want - you end up rushing your model into mediocrity.
To that end, you might want to consider getting reference of simpler objects to start with. I would suggest that what you want to do is improve your modeling “vocabulary” - your ability to create complex shapes in an efficient manner. Right now, you’ve got extrude and bevel figured out, but you’ll want to learn how to “see” how to build a particular shape through a series of steps. Every day items - like a pencil or pen, or faucet, or dropper bottle, or a key. These aparently “simple” objects can be great modeling exercises when you pay attention to all of the real details that are there - they appear to be simple objects but they are a microcosm of details. The skills you learn by taking the components of, say, a mechanical pencil and building out each part with all of it’s detail, will translate into better observational skills, which translates into better modeling skills, and more artistically pleasing models.
I also recommend just screwing around with the modeling tools - I consider that “working out” in any modeler. It helps build muscle memory, and occasionally you’ll find some weird technique that you will be able to leverage later.
Any journey of a thousand miles begins with the first step. The artists you see here creating such beautiful work were, at one time, sitting right where you are. They worked through the awkward stages and persevered - always working to get better - learning from other artists - emulating what they see and then adding their own twist. A great way to learn is to try to recreate the work of others. Once you have the modeling “vocabulary” built up, you can move on to creating your own unique visions.
Sorry for the novel. Best of luck to you - and remember that you will never be “there” - art is a journey, not a destination 
I would also highly recommend this presentation by Gleb Alexandrov at BlenderCon: https://www.youtube.com/watch?v=0KhJrMKo04g
