Congrats on venturing in the CP world!!!!!
It's a lot of fun and rewarding!
Personally I prefer the soapcalc lye calculator. It has the liquid amount given that you don't need to worry about. If your more experienced you can lower that amount, but for a beginner soapcalc is much better. It also great for the benchmarks when you take the time to learn how to use them. http://www.soapcalc.net/calc/SoapCalcWP.asp
When making your first batch of soap I suggest that you use a recipe that is tried and true and not one found on the net net on someones blog from someone who makes one batch of soap and thinks they know it all. There are a lot of BAD recipes that are NOT balanced on the net. The oils and the amounts do make a difference.
Learn to make your recipes in percents instead, it's much easier. Then convert them to the recipe size that you need. It makes a difference because if you try a small recipe out and like it you can then make that exact recipe larger and it will be exact, not just close.
Milk cartons can be used as a mold, just cut them off on how tall you want your soap log to be and make it vertical instead of horizontal. Then you can cut them into squares. Cover the top with some press-n-seal, it's like saran wrap but it's sticky on one side so it will work nice on a milk carton. You can line it if you want to but you don't have to because it's already wax lined.
You can also use other things like plastic drawer organizer or a box that you line with freezer paper. There are plenty of tutorials online on how to do this. I prefer to use a quilting ruler to make my liner for my fold lines so it's fitted exactly rather than close. But you can also line the milk carton if you want to and use it over and over. I have not used a milk carton before myself. You can also check out thrift stores or rummage sales (or buy new in stores) for silicone food pans. Such as a loaf pan or muffin pans. They work great for soap and it's easy to remove the soap from the mold. Just don't use them for food once you have used them for soap!
To figure out how much oil to use for your mold you use this math equation.
If you use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
You take length X width X height of pour, that number X .40
12 X 3.5= 42
42 X 2.5= 105
105 X .40= 42 ounces of oils needed for this mold.
Or you could use this re-sizer calculator.
If you need help with a recipe post what oils that you have to use and I can help you with a recipe that will be good with the oils that you do have to work with.
But if you ever do use a recipe found online, never use the lye and liquid amounts given on the recipe. Don't trust the info posted for that and always run the recipe through a lye calculator yourself to get that information for yourself.
Last but not least, even if you don't dress up like your going into a radioactive area, I personally don't wear long sleeve shirts (sometimes I wear tank tops), and I rarely wear gloves but I ALWAYS and I mean ALWAYS wear goggles or eye protection. Please don't ever make soap without eye protection. If you do use gloves I suggest the blue nirtrile ones, you can buy them at walmart cheap enough. They won't break down like latex gloves if oil touches the gloves.
I also don't keep a gallon of vinegar at hand, but if there is a drip or spot I just dilute it with plain tap water by washing my hand or arm or whatever got splattered. But I do know where my vinegar is if I need it, which IMHO is if there is a major spill, which I haven't ever had yet in hundreds of batches.
Anywho I'll just leave it at that, if you have questions do ask....