For your minimal book cover, I’m not sure all your sample fit that definition. The photograph covers are nice, but I would not say they qualify as ‘minimalist.’ (I can forward you to a short video that might help provide a different way to look at it.)
The brand identity gig, I can tell you were trying to tie the 2nd and 3rd images together, but there’s no indication of this. Use an ellipsis ‘…’ to indicate that the statement is continued AND to start the next bit. (Also, capitalization.)
The ‘WISHES’ logo also needs a bit of fixing. If you’re going to use stacked letters, you need to make the letters themselves more blocks, and align them individually vertically, too. (The book cover that uses this stacking too also looks misaligned.)
You say your still working on the logo gig, so I’ll skip that.
The blue font and black t-shirt vanish into the dark grey background. If possible, lighten that up so that the words and Ts pop. Lower the white ones down if you can, on both images, as the negative space below them attracts too much attention. Don’t be afraid to overlap, as for this instance, that will give the image a feeling of depth (if you know how to add ‘shadow fuzz’ be sure to do so as needed.) Unprofessional caps-lock in description.
Like in the previous gig, the white text vanishes into the bright blue. This one is a bit trickier to modify, as I can tell that shade is intentional in order to match the stripe on the shirt. It might be easiest to fix with a semi-transparent stripe behind them. (You might be able to make the stripe look like the smudge on the T, to help tie them together more. I have no clue if this will still look good, though.) The white Ts in the last image vanish into the background.
Last gig, more vanishing.
For all your gigs:
Your gig descriptions need to clearly differentiate what perks are part of which package. (If a buyer is confused, they’re more likely go elsewhere, rather than take the time to puzzle out what you’re offering.)(The first sentence in every gig should echo its title, to reaffirm what you’re offering to do. Window-shoppers have a short attention span.)
Always check your gig thumbnails from your profile. This is the best way to check how people will see your gigs in the search lists. Keep in mind: The text (size, font, color, style, location) needs to be readable. Shrunk images don’t always look as good as the full-sized. (These are usually the first thing people will see, and a poor first impression will drive people away.)