Fluids are a MUST. If you don't have ANYTHING else, you MUST have fluids and IV lines. You need to learn to get your fluids in the vein and not under the skin. If your dog is in bad shape, under the skin is better than nothing, but it's still almost nothing to a dog circling the drain.

Dex isn't needed near as much as people want to use it, though it can be nice to have.