So I'm converting the small nook off my kitchen into a full bath if possible. The space if very tight about 4'9"x5'7". I'm trying to figure out how to fit small components into it. Seems the smallest shower is about 32", and the sink will likely be a corner sink (31"x24") on the same wall, adjacent corner as the shower. I'm leaving the other adjacent corner to the sink for the toilet. A 24" door (opening outward to the kitchen) will be adjacent the shower. Bathroom fixtures, stalls, vanities/sinks are extremely expensive these days. And those aren't even the highest quality items (Home Depot/Lowes). I'm trying to decide if I should put tile in behind the shower or use a kit; because the kits aren't cheap.
The dwv plumbing lines take priority over everything, for the toilet especially. You have to look underneath and plan how you will run the 3" waste line for the toilet and how you are going to tie it into the main sewer line of the house, and it has to pitch at least an 1/8" per foot. All three fixtures have to be vented as well, so you need to figure out how you are going to tie the vents into the stack.
If you are going to go with tile, (and I suggest you do not, for a low cost easy bathroom), the floor framing will need to be beefed up. I reframe every floor for every bathroom, because in the end, it's easier to just rip it all out and reframe it properly, and frame boxes for the toilet and shower plumbing. Framing for tile floors and walls have to be dead flat and stiff. If the floor has too much deflection, the tile will crack.
Building a waterproof shower is not easy. If you screw up one small detail it will leak, and there's no patching it up, it will have to ripped out and redone. Unless you have some experience in this area, I strongly suggest a fiberglass shower stall. The biggest mistake when installing them is having them squeak when you step in. If you still want tile, another option is a fiberglass base with tile walls.
Make sure you have enough room around the toilet. You need about 16" from the center on each side, or it will be uncomfortable for people to use.
If you put a vanity in, make sure the doors can open freely without knocking into anything.
The shower is the biggest space taker upper in a small bath, see if you can steal some space from whatever is on the other side of the walls in the nook. Sometimes you can build the shower into a wall if there's a closet or hallway on the other side.
For something like this you need to do a lot of planning. Figure everything out down to the last detail before you start building it.
