[WARNING: Long post with hopefully helpful advice inside. Don't tl;dr. Stick it out if you really have the passion to improve.]
I think you may not give yourself enough credit, Tdatapina. Writing isn't something that miraculously manifests itself as a publishable manuscript waiting to be poured out of your mind, through your fingertips and into the computer. Finding you repeat yourself, or use certain words too frequently doesn't make you a bad writer, because those things can be fixed with simple editing. Identifying them as points in need of improvement means you're already halfway there. A bad writer is someone who never bothers trying to improve. It's a skill that takes time to master, and can always be improved, but you can't get better if you give up before you try. Asking for help in this thread means you're not willing to give up on yourself or your writing, and that puts you ahead of those who would rather complain than work at it.
I know it can be difficult to look at what you've managed to write and not feel some disappointment when it doesn't match what you felt while writing it. One of the first revolutionary pieces of advice I received that changed how I look at early drafts is "The first draft is crap. It's meant to be crap. Accept it and move on."
I didn't want to hear that. I didn't want to think it of my writing, and it took a long time before I could understand the real wisdom behind it. A first draft is word vomit -- it's you exorcising the story from your mind, a purge of the initial creative juices. Purges aren't pretty, but they are important. The purge is the foundation of your story, without which you have nothing to clean up, and nothing to clean up means no story to share.
This sets up my first two major points of observation and advice: Don't approach writing like a reader, and the writing is in the editing.
To address the first, a reader picks up a book to experience the characters and story, and when they're done is often ready to move on to the next. Those who write like readers often express distaste for planning stories, and prefer to be surprised by the directions they take as they write it. They struggle with editing, because they've already lost interest in what they've experienced and uncovered, and feel disinterested in forcing themselves to read it all again just to make it pretty. They're more interested in pouring out the next thing that inspires them in order to see what happens next. Mixed into this is the displeasure of seeing the quality of early drafts fall short of their hopes or expectations. It's difficult to improve the writing if you refuse to fix what's wrong for lack of interest.
Sometimes it helps to change how you view the process, though. Writing is in the editing. That is to say, what most people consider to be editing -- a task many writers find tedious and hard to work through--, is the true writing process, and what people call writing is just the word vomit of an outline. If sculpting was all in throwing a lump of clay at a table or taking a hammer to some marble, we wouldn't have things like Michelangelo's David, and the same is true of writing. Word vomit is an early draft -- it's your uncut stone, your pile of clay--. and what you currently call editing is how you clear away the metaphorical chunks of brain juice into the story you see in your mind, how you shape the clay or carve the stone to reveal the sculpture you see in your mind.
With inspiration, Amaryllis has the right of it. Inspiration does come from all around us, and it is how we use that inspiration that separates an original work from a copy. You'll hear said to death "There are no original stories," or "Every story that will ever exist has already been told," and in many ways it's true. Some people take this to mean they shouldn't try telling stories anymore, but it's only meant to illustrate that originality has very little to do with success or creativity.
To use a big budget example: Avatar is just a spacy retelling of Pocahontas. For some people, that was a major mark against it, but for many others, that truth never factored into their enjoyment of the movie, or lack thereof. Using something old or familiar doesn't make you derivative, unoriginal, or uncreative. Using familiar elements and inspirations often makes it easier for readers to connect with the characters or material, which is definitely something you want for them.
For a good while I cleared away every body I killed in Skyrim, hiding them away for the sake of keeping my character's activities clandestine as possible. During one of these moments, I envisioned a conversation and scene between my character and a follower, but I hadn't yet gotten to the point where I felt I could write a fan fic. To me, this meant I had to translate it into terms I could use for my original works -- the concept, the conversation, the action, these were all things that came from me, not from Skyrim, not from Bethesda or Zenimax, or their writing teams. The setting, the name of the follower with my character, these things were theirs, but the story was something I dreamed up. Inspired by their work, set inside their work, yes, but still all mine. This meant all I had to do was change how I viewed them, where I viewed them. I dropped them into a fantasy world I'd been building for a long time, imagined it as a scene happening in the midst of a life I hadn't fully developed. It added a lot of color to a character I hadn't fully explored, and gave me a lot of new ideas to consider.
You can find it here, being possibly reminiscent of Skyrim, but still entirely independent.
Something we as writers can't avoid, no matter how well we consider our characters and plots, though, is putting a piece of ourselves inside them. Part of it involves the concept that no matter what you imagine, or how far you try to reach outside yourself when making a character, you're building it out of your ideas of what is contrary to who you are. That's still a piece of you. In many other cases, we build them out of challenges we face, obstacles we strive to overcome, victories we value, qualities we admire, because if we can't connect with our characters, we struggle to convey who they are -- their hopes and dreams, their goals and desires-- to the reader. Sneaking a piece of ourselves in there is our first foothold to understanding them so we can show others how to do the same.
Knowing this, sometimes it can be easier to build a character by picking an aspect of ourselves -- an aspiration, a shortcoming or flaw, a fear-- and building a character around that trait. When I was in high school I built a character around my fear of appearing vulnerable to others, and desire to feel strong regardless of the situation. I have a character built around exorcising a sense of betrayal, feeling trapped between two opposing people, finding myself, my obsession with the pursuit and preservation of knowledge, my sense of loyalty, etc. Characters aren't just born from needing to fill a hole in your plot, but may spring from a part of you that resonates with something within that hole.
Literary characters are meant to be simplified and slightly exaggerated so people can quickly understand and identify with them, to predict or understand the choices they make along the journey. This is not to say they can't be complex, or represent complexity, or that either of those is a bad thing, but that filling a character with as much complexity as resides within you can detract from the plot, and a character's complexity should not be more important than the plot or goal of your story.
Ultimately, there is no single method I can show you to get better, because everyone needs something different, everyone uses writing for something different. Discovering what that is for you is part of what makes your writing yours and not a knockoff of someone else's.
Some good exercises involve flash fiction, though. Limit yourself to telling a story in five hundred words. If you can't use five hundred words effectively all by themselves, how effectively do you suppose you can use several thousand? Given the freedom of no word limitations, we can wander, we can fill the void of the page with an endless parade of useless information and description that serves no better purpose than to take up space while we try to figure out what we really mean. View words as your currency; they're a limited resource, so spend them wisely to convey what you need without waste. Forcing yourself to be this sparse tightens the prose, it demands you think about what you mean, what you want to say in the space you have, and eliminates the unnecessary bits.
Another exercise is to pick a prompt, like "Write from the perspective of an inanimate object", and write for fifteen minutes. I like to use nine or so to write the story, then the last six to edit, but even if you use the full fifteen to just write (the word vomit way), you still work toward telling that whole story in the time allotted, and it gets easier the more you try.
Sometimes advice comes in bite-sized chunks, and other times it can't be so easily condensed. Writing is a pursuit, even when it's a hobby. I consider myself an accomplished writer -- it's been a life-long passion, and it is my career--, but there's always something to be improved, some way to make it better, something new to explore, and no matter how much I feel I've improved, I know there's still somewhere new to go.