Your first lotion is going to cost money. Creating your own lotions isn't an expensive hobby, but the initial outlay will be the most expensive!
You will want at least one oil, possibly a butter, some emulsifier, a thickener, a preservative, and at least one bottle (and those things are expensive!) You are going to spend probably $30 by the time you are done (oh, and you'll want at least one fragrance oil, but you'll find a few you like and you will buy those as well, so make it $50). It is well worth it -- if you consider that 100 grams of lotion needs about 5 grams of e-wax and 2 or 3 grams of thickener, you'll realize you aren't using a lot, but no one sells 5 grams of e-wax or 3 grams of stearic acid or cetyl alcohol, so you'll have to buy at least 30 grams of each. So your first batch is going to seem expensive. Don't worry -- the 30 grams of e-wax you buy will make at least 1/2 litre of lotion, and you'll love the initial batch, so you'll make more, then before you know it, you're buying e-wax by the kilogram.
So I write this to save you money and save your sanity! I want lotion making to be fun and exciting, not annoying and frustrating!
1. If you are adding water, you need a preservative. I have found sites that consider preservatives optional -- this is foolhardy at best. I know that some people consider using preservatives on par with killing puppies, but they are useful for a reason. Unpreserved lotion can go moldy eventually (because the water is not necessarily sterilized) but it's the beasties you can't see lurking in the lotion that worry me the most! I would rather take the risk that the well tested preservatives might bother my skin than to slather on piles of bacteria and mold and have a serious reaction to that. (Some tutorials suggest keeping the lotion in the fridge. This might slow the rate of bacteria or mold, but it won't stop it!)
2. If you are adding water to oils, you need some kind of emulsifier. (Water includes water based products like hydrosols, witch hazel, and aloe vera). Water and oil don't like being together -- try putting some oil in a cup of water and you'll see what I mean. An emulsifier is a product that brings the oil and water together and keeps them together in a cohesive way. A typical emulsifier will be Polawax, e-wax, or Incroquat BTMS (or BTMS). If your planned recipe doesn't contain these things, then it might contain beeswax and borax, another emulsifier some people use. If you don't see those things listed, don't bother making the recipe.
(Note: I recommend buying Polawax over e-wax. E-wax could be a variety of things; Polawax is always Polawax. It is more expensive by about 20 or even 30%, but it works very well and worth the investment.)
3. If you are making an anhydrous product, you don't need preservative or emulsifier, but you might want to consider adding an anti-oxidant like Vitamin E. Anhydrous means "without water", so a product that includes only oils, butters, waxes, and the like. Lip balms, whipped butters, salves, balms, and other all oil based products. Because you don't have water, you don't need a preservative, but you may want to consider adding Vitamin E at 0.5% to keep the oils from going rancid. In short, the oils we use are unsaturated, so they can go rancid in less than a year. (Some have very short shelf lives -- grapeseed and hempseed are 3 to 6 months if you're lucky!) Rancid oils are seriously icky, so adding some vitamin E can extend the life of the balm, salve, or whipped butter by quite some time. If you aren't going to use an anti-oxidant, then just make small batches and put a date on it!
4. Please do not re-use containers! Perhaps for your first few batches, it's not a problem. But never use a jar someone else has given to you because you don't know what they've done to it! When I run classes, I've seen old pickle and other food jars brought to store lotions and bubble baths -- ick! If you lack fundage, then consider the dollar store for your bottles or buy a box of canning jars and use those. Even old bath & body containers can be icky -- if there's even a tiny bit of oil left over from that last batch of sugar scrub, it can go rancid!
Please don't let what I've written scare you from making your first lotion or, indeed, trying other tutorials. The first time you see a lotion come together...well, it's simply awesome. And to know you can adapt lotions to your specific needs...again, awesomeness prevails! But there are so many poorly written tutorials by people who don't completely know what they are doing out there, I thought I'd give you some pointers to separate the good from the awful!
(For great recipes, check out the Dish and Voyageur Soap & Candle -- linked to the right!)