How to Survive DLC ?

I doubt any of it is at all essential, but with the sale right now it'd cost $1.34 to buy all of em.

All of it is pretty much on your own taste. The alternate costumes supposedly give fire-resistance which is VERY useful but the rest of the DLC is just a new character, different modes (survival is probably my favourite, it has a nazi-zombies-ish style of gameplay except you have to protect a single object and not just yourself).

EDIT: Oh, yeah, there's also the three new islands which really doesn't have anything interesting to add other than the island-exclusive ( because you recharge it at locations on the island or via lightning ) electric gun.

I don't know. If it's some sort of disease, then You should isolate Yourself from the whole world, drink only water and eat canned food. If it's some beast, then collect a lot of food, water, guns and toilet paper and block Yourself into some strong place. Though, I don't know any disease or beast that's called DLC.

Just a rule of thumb, if there is a huge sale on a game and it's DLCs (especially if there are quite a few of them) then it is more "savvy" to might as well buy the DLCs so you save money later. Especially in games like Fallout NV where buying all or any of the DLCs separately is super expensive, and once you bought the base game you cannot activate the "Ultimate Edition" on top of it, so you have to buy all the DLCs painfully piece-by piece. Then there are the f***ng insane games where they went absolutely berserk with the DLCs like Crusader Kings II, I don't even....

Anyway TL:DR I'd get the DLCs