Title : Konosuba Character : Aqua Coser : Baobao Cosplayer
(2/2) Also, is there a way to build it while still being convenient for travel?
Foam would be a good choice for the top portion of this build, yes. I wouldn’t go with what you are thinking of as styrofoam, but rather a different type of styrene foam – XPS foam, aka ‘pink’ insulation foam. This can be carved and sanded into shape, and then sealed so it can be painted. This would get a very smooth look. You may need to make this in two halves and include some curved structure on the inside for a bit of added strength.
I wouldn’t recommend something as heavy as paperclay or air dry clay for a build this large, but if you want a more heavily textured wood look, using a thin layer of clay over a base of foam would be able to be sculpted into a wood-like look. I see some references (this one looks like fanart but it’s a good example) with a smooth staff and some with a more textured staff, so this would be an option for a more textured staff. I made a “wooden” staff a while back with a similar method, and it created an effect similar to the more textured art I’m seeing around.
Where you are really going to sell this prop is in the paint job. You can buy tools meant to create a wood grain effect, though I haven’t tested these around curves. Here’s a tutorial on how to make something with more texture look like antique wood; you can change the colors up a bit to make it less antiqued, so that it’s a bit brighter. If you are using an actual stick as the base, be sure to match the colors so it blends well. If you are painting the base, that won’t be a concern.
To make the orb float, if it is lightweight enough, fishing line will work, or you can use thin acrylic rods to stabilize it.
For the staff itself, you have several options. If going for the more realistically textured look, an actual wood stick is a good option, and can either be scavenged or purchased. If you want something smoother, a wooden closet pole or PVC would be good options.
To make it separate for easy travel, you can sink a screw into a wooden pole, or you can make separate tubes that slot together. (See this recent post for a few tutorials.) I would do this just above or just under where the wrapping is so you don’t have to worry about the cloth having a seam in the middle or re-wrapping the handle, since the seam will mostly be hidden by the joint between the cloth and the wood (or “wood”). If you want to do it in the middle of the wrapping so it is more likely to be hidden by your hands, either secure the wrapping well on either side, or leave a small trailing bit on one half and a way to attach it (such as a snap or a place where it can be tucked under the rest of the wrapping) to hide the seam.
I hope that helps! Good luck :]