iron mahou, from its description, sounds like you have a lot of potential to be very genre aware and have some interesting crossovers of magical girls with superhero lore and... playing cards? the term 'rares' intrigues me. the idea of a world where magical girls are common as pigeons and some are involved in secret spy operations sounds like a modern superhero comic's lore, which is something ive never seen before in the magical girl genre. thats really cool.
your art is really nice; a fairly genre-typical style with a good understanding of shading and colour, its very pleasing to read. id be interested in seeing you vary your characters faces more - i understand that the style and genre is typically very same-face but i think making facial variation work could really unlock something in your work. also, in the cover where shes sat on the steps, shes not very well integrated into the scene - it kinda looks like shes been dropped onto it, because of the way the shadows fall. youd do well to focus on where your light sources are (in this case, a strong light from behind) and carefully considering where that light will fall. a lot more of that pole should be shadowed by her arm, and with light like that id say her, her food, and the crow would be casting very long, fairly harsh shadows (which would also look pretty cool.)
your panelling is interesting, varied, and flows well, with a good use of different panels, and your lettering is very clear. really, nothing about your work reads rusty in the slightest, im sure youll have no problem developing an excited following.
you mentioned struggling with dialogue - this might be an obvious tip, but just in case - steinbeck always recommended saying your dialogue out loud, n i find it helps me. it makes it easier to identify the places flow jutters, or when words are overused, and can make it easier to develop a character Voice which makes it so much easier to write dialogue.
since you say youre a newbie at comics, id recommend reading the scott mccloud books on comics. theres some pdfs lying around online, at least of 'understanding comics' (followed by reinventing- and making-) theyre really helpful references