I'm a newbie myself, so please take my comments with a pinch of salt
For the first and second photo, the background is quite distracting, so maybe you could try out a prime lens at wide aperture to help blur out the distractions with narrow depth of field, or somewhere with a "cleaner" background.
The third and fourth photo are better than the first two, and the fourth one with the nurse is really good, with the composition and the perspective. The handrails ate a little into her shoulder, so you might want to avoid that in the future.
For the last photo, the sunlight was a little harsh and it is not flattering to the cosplayer. Maybe you could try using a reflector to fill in some light if you have to shoot in harsh lighting.
Most of the photos look a little underexposed to me. If you plan on sticking to this hobby for a while and spend time post processing, maybe you can invest on a monitor calibration device like the Spyder, to better gauge the brightness and the colors.
Thanks for sharing, and keep shooting!!