The basic gear you will need when facing the great outdoors
First off, I'm not Bear Grylls, nor am I a Marine trained to live in the jungle for weeks on end. However, you can rest assured that through the years of camping, traveling, being a scout and living in the country, I've absorbed a large inventory of knowledge in regard to what you need to bring when facing the great outdoors.
Water : Duh right ? Well what happens when you run out ? You can't simply carry galons of water on you, and in the event you find yourself out of water, you need to be equipped to adapt. Invest in a pack of water purification tablets. I bought the Aquatabs pack of 30 many years ago and I still have a few left, and they work. Trust me, I dunked my water bottle in nasty swamp water the first time I bought them, threw a capsule in there and 10 mins later chugged it. I tastes bad but it works
Knife : Buy yourself a quality knife. I would recommend the classic Swiss Army Victorinox, since it comes with all sorts of accessories, but a regular fixed blade, full tang will do. Don't be stingy, some would stress the knife is your No.1 survival tool. Gerber is a good brand to trust.
Waterproof matches: No matter what environment you choose to explore, always bring fire. Also if you have the space in your backpack, bring firestarters. Also, learn how to make a fire without the use of gasoline, oil or any other fuel ! Practice knowing when a fire needs oxygen or more wood.
GPS - Compass: Always have a compass, and if you do not know how to use one, buy a GPS. Nowadays they aren't very expensive and are very accurate. You no longer have to pay per month with modern GPS.
Basic First Aid Kit: Can be found in most pharmacies or online. Include bandaids, rubbing alcohol pads, disinfectant pads, sterile combine dressing and gauze pads etc.
Signalling : If you end up lost, you need to be able to communicate your situation with any other human beings in the area. Always bring a whistle and if you can, a mirror to send flash signals to people far away, as well as helicopters and boats.
Remember, be weatherproof - Since this is a breif overview, I cannot advise on every single type of weather and tempatures you will encounter. Use common sense. I spent a few weeks walking the Camino de Santiago in Mai 2010 and was told the weather would be on the mild-hot side. We got there and there was a snowstorm ! I mention this simply to say that you cannot prepare for everything, especially if you need to fit everything in a backpack. The most common mistake made by newbies is to overpack.
Be safe and enjoy the freedom of the oudoors !