I just got in my order couple of days ago, and got from basic to intermediate stuff, i guess.
1. Nicotine. You can get it in multiple strengths. Order stronger than what you want to vape at, because your flavorings, PG, and VG will dilute the nicotine strength. The stronger the nicotine, the more expensive it is per ML, but each ML will last you longer, because you'll use less in each recipe you make. I vape 6mg in my RDA, and 12 in my tanks, so I ordered 60mg/ml nicotine. To make a 10ml bottle of ejuice at 6mg, i'll need 1ml of the nicotine, and 9mls of flavorings, pg, and vg. Makes it easy. You can get it in a PG or VG base, some seem to think the PG base helps preserve the nic longer. Your choice - if you're making MAX VG juices, you'll want your nic in VG.
2. Propylene Glycol & Vegetable glycerine: available from a number of sources, I used Wizard Labs as I was getting my nicotine from them already and wanted to make it up to free shipping. Available from a number of sources on Amazon, as well.
3. Flavorings: Wizard Labs has a huge selection, at fairly good prices, in small vials. Good for starting out - 1.49/1.99/per bottle is not going to break the bank.
4. Syringes - You'll want a couple of larger ones (5 or 10ml) for your PG/VG, and smaller (1ml) for your flavorings. I went ahead and ordered a bag of 100 1mls off of Amazon, and they work great - I can have a separate one for each flavor.
5. Bottles - order more than you think you'll need. I bought 10ml for making juices, 30mls for the juices I really like, and just ordered some 5ml to give out samples to friends
That's it for basics! It is an initial investment, but you can make a ton of juice for very cheap. All together (even with the 30+ flavorings, bottles, VG/PG/Nic/etc), I spent around $175, but I have enough to make 1000mL+ of liquid. That's 33 30ml bottles, at around $5 each; or 100 10ml bottles at $1.75/ea - and I normally pay $6-7 for the same size bottle from vendors! It'll only get cheaper as I buy more.