Just wanted to chime in on the whole PS/PDN discussion.
Not only does Photoshop have more features, it also provides higher quality images. Scaling in photoshop is insane compared to PDN, and overall ‘fluent-ness’ of the software.
As for your work, there’s not much I can say that others haven’t. It’s a good start, and with time you’ll be amazing. Lighting as others have said is my main suggestion to work on.
Also there’s student discounts available for the abode suite making it much cheaper than normal, not sure if there’s the same discounts for PS alone. I personally pay $16/m for the entire adobe suite.