As its name says apple cider vinegar is made out of apples. Amount of apples that you use depends on how much space and time you have. If you have bigger dishes and place where you can keep them, or if you spend a lot of vinegar, then you can make vinegar from more apples.
The biggest problem is to find organic apples. If you don't have your own apples or don't know anyone who does, it will be difficult to find real organic apples. All apples are treated, more or less, with some kind of chemicals. Surely, for vinegar you will not need the biggest and the most beautiful ones. Choose the cheapest and less beautiful, just watch not to be dried or rotten.
First, you have to wash and clean them. Throw out the seeds. Now you have to grind them in blender or some other way. Put the grinded apples in the barrel or a jar (depends on how much apples you use). Now you have to squeeze apples to let their juice, you can do it with hands or with the bottom of a glass bottle.
When you squeeze the apples, pour water over them. Before that you have to dissolve sugar in water (for 10kg (22.05 pounds) of apples you need about 400g of sugar and at least 4l of water)
If apples are sour or unripe you should put more sugar (900g for 10kg (22.05 pounds) of apples). Actually how much water you will use depends on how juicy apples are. If you put more water you will have more vinegar, but vinegar will be milder - that should not be your goal. The water is added because it is important that apples are not without juice. They must be in the water or in their own juice, they should not be dry.
If there is no liquid there will not be vinegar and beside that if the blend is too dry there are better chances to get spoiled. Keep in mind not to fill dish entirely because blend could get out. Leave at least 1/4 of the dish empty.
Dish with apples cover with gauze. Do not keep the dish sealed because you don't need alcohol only vinegar.
Sugar is an important ingredient for fermentation. It is also important for bacteria growth, which in the end will give vinegar from apples and sugar.
Apple fermentation takes about ten days in a warm place (you can put them on the balcony on the sun). At the start when it starts to ferment, apples will swim on the surface. A sign that the fermentation is completed is when apples sank at the bottom (under one condition - if you pour enough water, as I said at the start). Take ten days, roughly, it depends of warmth. If it is hotter the fermentation will end soon.
When it ends ferment you should filter vineger out of apples in the bigger glass bottle. Filtered vinegar should keep in cold and dark place like a basement or storage room.
On every ten days you should filter vinegar through gauze into another bottle, to get cleaner vinegar. This is the process for what you should have nerves and patience, because it needs to be repeated several times. The more times you filter your vinegar it will be cleaner. Also, it is normal that on the surface of the vinegar forms mold and you should throw that when you filter vinegar.
Vinegar is ready for use first time you filter him, but as a wine if it stays longer it will get better, it will taste and smell better. Since I made vinegar for years, currently I use vinegar which is two years old.