I'm no expert or pro. It looks like your kitchen has mint green walls and white cabinets. Dark colors can make a room look smaller and it looks like your kitchen doesn't have a lot of natural light, so that's another reason to avoid dark colors. I like the blue tiles but am concerned they might be a bit dark. What about these ideas?

The horizontal line on these tiles could give the illusion of a wider room.

I think this could look stunning with your white cabinets. As far as the countertop, I've seen shows on HGTV where they've purchased a slab for a countertop and said it was "fairly inexpensive." You may want to search Pinterest for ideas. I'm glad the kitchen isn't walled off, so to speak. I've seen some small kitchens that have a wall blocking the view into the living area and seems like a punishment to have to go into the kitchen and cook. Good luck!

Edited to add: You may want to cross-post this in the Kitchen forum for more ideas.

I would not be afraid to use dark colors. in my opinion and experience "dark colors can make s room look smaller" is not really the case. You could also do light and dark together.

counter top - there can sometimes be great finds on Facebook Marketplace, Craigslist or Habitat Restore (If you have one local or something like it, I've gotten nice granite and laminate pieces from these places). same for tile, Home Depot and Lowe's can have some nice tiles and prefab laminate countertops or skins ( you reskin your tops).

Post this over in Kitchens and also Home Decorating. More traffic.