I find best to tranq dart and starve tame and i will say buying kibble or making it is worth it. Gallimimus kibble this can saive an hour or two. If you're looking for one go south zone and where there is a beaver dan there is usually a beaver. Quickly grab the stuff from the beaver dam this will agro the casteroides . Either pick it up with an argie or run and shoot. I havent actually tested a bola on them but they look small enough, good luck. Its a high reward after taming these B- Gates werre times easier
The method I used to tame was picking up the beaver with my crystal wyvern and dropping it in a taming pen. Pretty easy knockouts but their torpor drop rate is INSANITY and you can't leave then for more than 3 minutes. Feed them either mejoberries or crops (kibble is really expensive but if you want to do that, go for it).