Outfit keeps spiking in the gallery and CAS icon.

This is for the female hanbok package, and I pretty much followed the same process, checking for mesh groups, deleting the ones I don't need. The mesh I cloned with did not have any skirt bones so I deleted the skirt bones from the hanbok and it started spiking like crazy. I restarted and kept the skirt bones again and the spiking went away but there is still some minor spiking at the bottom:

drive.google.com/file/d/1OJ4Lqxio9n-k9jdMSUNAVXq0dv67lTO1/view?usp=sharing

Not sure what might be the issue this time? The package is below:

drive.google.com/file/d/1h2WsNMOl_Nrh_rKhrkcmt5FAWdkwnRRu/view?usp=sharing

The spike happens in a place where the introduced bone is. So you need to select a few vertices in that area to see what bones they are affected by. If you see a bone that is not present in the original mesh, find it in the list, select it, click on Select to see what area it affects to make sure it is the right one. Then just remove it and normalize weights

1.The original dress is not rigged correctly, some thigh weights are missing. You must retransfer the weights.
2.You must split the mesh the same exact way the original item you started the package from is split.
3. You need to deleted only the bones that are not present in it.

- clone iuBody_EF48PajamasMonster again, export as Reference, open;
- toggle the eye icons next to each meshgroup to see that it is not split the same way;
- File - save as "lod0.blend"
- join both meshgroups, rename to Reference;
- transfer weights from the reference to the blend this way, the process differs in 2.76;

- hide R0001, select Hanbok, select the same area of the hanbok that 0000 contains, separate with P - Selection, give it the same cut number, delete both R0001 and R0000;
- give the other meshgroup 0001;
- download and install Remove unused vertrex groups addon  ( type in 0, choose Purchase, follow the instructions. Open the file, move 270 on your desktop. File - Preferences, Addons. Install from file, choose .py). Remove unused vertex groups on both meshgroups;
- save, import back into iuBody_EF48PajamasMonster

For hanbok, of course. It makes no sense to delete the data that you need to transfer to another item
Hanbok must have no hands or neck yet. Never transfer any data to body parts, they already are perfectly adapted

You join the body with the garment once you need it. In your case it is after the weight transfer.
If the reference is suitable to serve as the body, then you can use it after deleting everything covered by the garment. In most cases it is not suitable (skirt too long, sculpted sleeves or collars, etc), so people use a different mesh for the body

I have a tutorial in my signature that lays things out step-by-step. Please note that I'm in the process of updating it, but in general, if you need a list of what needs to be done, when and how, my tutorial can provide that. I originally wrote this tutorial for myself because making CAS items is complicated and involves a lot of steps. It can get confusing. Whatever you do, always take Mauvemorn's advice over mine. 

I will tell you that, in my opinion, it is always best to start with a mesh that has no body parts attached, no weights, no vertex paint, no uv_1, no rig, no cut numbers, and is one complete mesh that hasn't been separated yet. I usually export this mesh as an OBJ file for that purpose and I hang onto that file in case something goes wrong and I need to redo things. 

One last edit to this post that I keep editing to fix awful grammar (lol): I discovered yesterday that my tutorial contains a dead link to the CAS map. If you don't already have this map and need it you can get it here. 

Thanks for the clarification. I think I misunderstood the toggle eye icon step. Am I toggling both groups off so they are hidden? Because I am unable to join both mesh groups after that when both are toggled off. If that is not what is meant in your directions, could you please clarify? Thanks again and sorry for not understanding.