A common issue that I see in people's bug out kits, go bags, or get home bags is just plain too many blades. Like an axe, machete, saw, two big fixed blades, two smaller fixed blades, three folders--that kind of thing. I like knives as much as anybody, but don't over do it.
What do you need? Your area and survival plans will dictate specifics, but in general, I would look at one capable fixed blade (4 to 6 inches in length), a sturdy folding knife and probably a bigger chopper of some kind--a machete, hatchet/small ax or a tomahawk. You could throw a folding saw in the "bigger" category, too.
A big blade like an ax, machete or hawk can do work that a smaller knife can't easily do, which is why there's a place for 'em. For chopping wood, the ax gets the nod. For urban use and hand-to-hand, a tomahawk would be your best bet. In a jungle-type environment, a machete can be a necessity.
If you do have that big chopper, I'd perhaps look at a fixed blade or folder that's more suited to fine tasks like carving, skinning, etc. Less beefy, more slicey.
For gear you're going to be potentially carrying over long distances, you really need to consider the tradeoffs in weight/benefit. How much extra use to you get out of that 3rd or 4th knife, when you could be using that weight for water, food or something else? The advantages provided by a big blade may not be worth the weight, especially if you need to move quickly and quietly.
Anyways, as mentioned, your survival plans should dictate. Think things through. Get out there and practice. Try different things and see what is most effective and efficient.
