You've got quite a lot of problems with this, actually. For starters, don't clone a swimsuit for your package, and don't use a swimsuit as a reference. Clone something that is as close to what you're making as possible and use it for your final package as well as to transfer your uv_1, and weights. I think you can transfer the vertex paint, as well, though I haven't tried it yet.
You've got parts of the neck poking through the collar so you'll want to adjust the mesh in that area, and the body parts are still inside the mesh. The hidden body parts serve no purpose and increase your polycount. Anything that the mesh covers up should be deleted. You will, of course, need the neck, hands, ankles, and lower arms of the body, but not anything that's hidden. If you delete the hidden body parts nothing will poke through the mesh when you use the sliders.
The skirt is double-sided and this, too, increases the polycount. Delete the inside and the rim of the skirt and close the hole, instead. Be sure to split the edges of the bottom of the skirt to avoid ugly shading.
Your UV islands are in the wrong spot on the CAS map. You can
download it here. Just right-click the image and save it to your computer. Hang onto it if you keep making things. You'll use it over and over.
You can bake the texture from your old UV layout to a new one.
Here are the instructions. Redo your UV layout. Once you delete the hidden body parts you'll have more room on the CAS map for your UV islands and you can make your islands bigger. This will result in a better texture.
Your uv_1 is wrong. It's holding your uv_1 islands
and your uv_0 islands. Those islands shouldn't be in your uv_1 at all.
Your vertex paint looks okay to me.
You'll need to make a bump map and a specular map.
I have a tutorial in my signature that you can look at for more info. It's geared toward Marvelous Designer but you can use any mesh for it. It's also geared for versions of Blender below 2.80 but the method isn't much different. In versions of Blender above 2.80, you don't have to use the clean function when transferring weights. 99% of what's in my tutorial comes from Mauvemorn. Always take her advice over mine. She knows her stuff.
