I think its going to happen, maybe not today, maybe not next decade but I don't have that much faith in humanity. So I prepare, albeit slowly. Prepare for natural disaster first(generally its the same story)
Have an evacuation plan in hand. Go find a map and do it, it takes 10 minutes to do a simple one.
First start with 3 day kits of food, you just keep in your car, your office, where ever. Takes about the size of a 1 liter milk carton (or just buy one). Good also to keep bottles of water around. I usually use MREs for main meals, but keep a few snacks in there. They make you happy, and unhappy people die. ^,,^
Next Build a mobile pack enough for 5 days of supplies. I use my hiking bag when it's not in use. First Aid kit, food for yourself for 5 days and water(I recommend having filters also because water is heavy) Toiletries, tent, matches, lighters. Poncho, warm cloths(depending on where you are) map and compass of your area (its not hard to learn how to use them, but learn before hand or you are fucked), 2 knife (I prefer a large knife like the Kabar because its usefulness around camp), knife sharpener. Sleeping gear, flashlights(I have 2, I recommend a flashlight that can be charged by shaking with LED bulbs)
Basically prepare for a 5 day hike out of your home town. I recommend getting a current scout hand book. Seriously I'm not joking, lots of practical knowledge about the out doors. Also some of the merit badge stuff is pretty good to teach you stuff. Like wilderness survival, archery, camping, ect. (I don't know what other countries have, I've read the American stuff.
Then prepare a vehicle born version of the above for 2 or 3 weeks on top of your 5 day kit. Your gas wont last that long, but it will get you to an aid station and you can survive off yourself before you resort to depleting aid supplies already being depleted by morons who didn't prepare.
Keep about a 6 month regular food and water storage. IE caned goods and nonperishables. Don't forget to rotate this stuff continually, use it up but always be sure to keep it stocked at the end of the month.
Then a one year storage full of stuff that will keep you alive and also keep for a few years before you have to rotate it.
Guns are cool, but I wont be surviving with them. Bows are practical -> learn them and shoot them regularly. I'd bet that most countries don't regulate heavily on bows, and even then they are pretty easy to make and hide.
Bow strings can be made with heavy string and ski wax. Bows can be made out of just about any straight piece of stiff and springy material. (wood cannot have knots in it as that will cause weak points and then you're bow is fubar) Same goes for your arrow shafts. Worry about arrowheads last.
Guns, I personally have one ready, more likely an old pumpy or hinged 12 gauge. Maybe a bolt action or black powder rifle, maybe a loose revolver.. Bad choices are high maintenance weapons. AR's are first on my list. Again if you are going to have a gun, know how to use it safely, you shoot yourself or someone you love it is YOUR FAULT. Use it a lot, go shooting. Guns are nether friend or foe, they are a tool, and in the hands of a master a tool is a wonderful thing. Know how to take care of your weapon. Clean it and keep it firing.
Basically you should first know safety, then know your weapon and how to take care of it, then lastly buy a box of ammo and shoot a lot.
Keep in mind, you aren't a hero, you aren't invincible. Don't go looking to use your weapon, use it ONLY as a last resort.
-----------------------NBC preparedness
There are a lot of resources at your disposal, biggest one being the Internet! I suggest checking out the Civil defense website.
Here is something to keep in mind while you are looking for gear. Buy it new. Usually the first mistake is buying stuff from your local army surplus. See that mask in my signature? Its from the 1960s/70s and it was used up until recently when it was replaced. I know its still in use by my local national guard unit. Its a good mask with modern filters. I DO NOT TRUST IT TO SAVE MY LIFE BECAUSE IT WONT. Why? because I paid 50 dollars for it at Uncle Sam's Surplus. Buy gear from places that sell MODERN equipment. Lets pretend you are looking to buy a gas mask. It should have been designed in the last 10 years, and I've never seen a gas mask that will save a life that was under 150 USD. You should know exactly how to use it. A gas mask can kill you if you don't know what you are doing. So you've bought your new M40 military gas mask(my gas mask for my NBC gear.). Hey cool, now have some one tell you how to use it and practice putting it on so you know how to do it in your sleep. Or worse, for real.
Sum up, spend several weeks learning about the equipment before you get it. You don't need to get it all at once, that will leave you broke and starving. Your biggest resource in any situation is knowledge.
YOU will be the only one to blame if you die because you don't know what you are doing.