Congratulations on wanting to get better! We're always happy to help, and photography is a fun way to enjoy cosplay.
You've found an interesting location for this character. It looks industrial and claustrophobic, giving me the impression she is in the middle of a tense situation. Thinking about settings is a good start.
Now - Turn off your flash.
Do not use your automatic flash. It is flattering to no one.
In Photo #1, it nuked your subject, overexposing her skin and giving her red-eye. It also cast all sorts of weird shadows and reflections (see the car taillights in the background? They're red because of the flash.)
In Photo #2, her skin and clothes are still washed out. The bar shadows are too tight and make the image confusing.
Turn it off. If the area is too dark to shoot, pick a different location or find a light source. In a parking garage like this, you would probably have to use external flashes (called "strobes") to get the setting to work.
Here's an example of a parking garage shot with strobes. The photographer, Elemental
, used off camera flashes to make interesting shadows and give her camera enough light to take the picture.
This is just to give you an idea of something to work on. Definitely keep shooting! Try taking photos away from convention halls, and look for brighter lighting. You don't need expensive equipment or full sun, but it can be easier to start outside.