I'll send you a link to (what I thought) was a very helpful tutorial on doing spikes with wigs [link] The tutorial comes in 5 parts and I recommend watching them all, she's pretty good about explaining and it's a really really good technique. Got2be freeze spray is AMAZING I can't push it enough. However do not use too much at once, you want to make sure you're doing light dustings with it, layering it up if you feel you need more, if you do too much at one time you'll lose the texture of the hair and it'll start looking really crunchy and fake.
My wig does not look like Goku's hair, it's not a literal translation, if you're looking to do Goku's hair more accurately you can try using carved foam shapes and layering hair over top of that
This is also a small tutorial for that kind of method [link]
This user: OtakuKawaii86 has done a Vegeta wig using the foam core method so if you're really wanting to do it that way I'd try maybe asking him (I have ZERO experience with this kind of stuff but I really really like how DBZ wigs come out using this, again if you want something more accurate I'd really suggest doing it this way)
How do you think this guy did this? [url][link] I can't really ask him because he hasn't been on in a while. It's his actual hair! [url][link] I figure maybe I could do whatever he did with a wig maybe. Foam sounds complicated :\
Something like that could easily be done with the first tutorial I sent you on spiking wigs. Got2be freeze spray is more than enough to make those spikes stay up especially if you plan on making them the same size as his.
Just go light on the product at first, if you find you arn't liking how it's coming out just wash the wig and try again. You're just going to lift sections of hair, spray the base with freeze spray to make them stand and twist the ends with hair glue, styling wax to get them into points, you can use scissors after pinching the points to get them to look sharper. Then at the end you'll go over the entire thing with hair spray if you're satisfied and it should hold up the entire day no problem.
Foam is probably a little more advanced, I havn't even attempted it myself so go with whatever you're comfortable with.