Some flavorings work better then others. Right now, for instance, I'm having trouble with LorAnn Root Beer and Apple. They just might not work for vaping.
As for oils? I would recomend the LorAnn candy flavorings but nothing else. LorAnn oils are mostly fruit oils and shouldn't pose too much of a problem. I would NOT recomend anything with a vegetable based oil in it. Burnt vegetable oils can slowly clog your airways.
Fruit juices? I've tried it. Tried to make a lemonade using Real Lemon lemon juice. It didn't work. The problem is (like Shadav said) that they contain either citric acid, sugars (natural or added), or both. The acid isn't good to breath, and the sugars carmelise as soon as they hit the coil resulting in a burnt tast.
You CAN, however, add a couple of
drops of lemon juice per 5ml of a fruit flavoring in order to inhance the flavor.
If your using stright VG I would dilute it with distilled water. You CAN use PGA but it might give your juice bit of a bite to it. Or if your using VG and PG you shouldn't need to cut it with water at all.
Extracts are tricky. In most of them the same rule goes as with the juices as far as their sugar comtent. I have however heard of some people making their own extracts by soaking vanilla beans in either stright PG or stright VG. But I would consider this an expert project.
Start with LorAnn, Mt. Baker, TFA and so on.
As for getting things from your local store? Here is how I started:
VG (Glycerine): From Rite Aid, Wal Mart, CVS, Walgreens ......
LorAnn Flavorings: From my local candy supply store, baking store, WalMart
Distilled Water: From Wal Mart
Liquid Sucralose (liquid Splenda): From my local grocery store, Wal Mart
15ml empty bottles: My local vaping store, e-bay, FastTech
Eye dropper: Rite Aid, Wal Mart, CVS...ect.
10ml syringe: Rite Aid ... ect. (look for a childs liquid medicine syringe)
All in all your looking at about $30-$40 to get started. But it is fun. And you'll almost never run out of juice.
Here is a thread involving simple recipes with only one or two flavorings in them.
http://www.e-cigarette-forum.com/forum/e-liquid-recipes/439217-simple-recipes.html
Have fun with it.