Building a horse stable by yourself is a great way to spend free time it can save a lot of money and it could be a nice family project. Timber for wood framing is readily available in lumber yards and you don't need a lot of tools, as a mater of fact you can get away with a circular saw, cordless drill driver and a few hand tools. If you pour a concrete foundation slab it is a good idea to have a drill with hammer option.
Choice of building materials is largely about preferences, you can build a stable out of concrete or bricks but my personal favorite is traditional looking wooden horse stable, that is not painted but protected by natural oil. On my opinion natural oil highlights the beautiful grain of wood. Of course the question that follows is what kind of wood should be used. Most popular woods for wood framing construction are spruce and pine, but on my opinion white oak gives a horse stable most exclusive look. However you you should consider which woods are locally available and if you own a forest, you may have some particular species that are more durable than spruce and have great looking grain.
It should be noted that best cordless drill is not most expensive one but the one that suits your needs best. That being said, best cordless drill for horse stable construction should have hammer option (for drilling in to concrete floor) and should be a full sized model as wood framing construction requires certain amount of power.
As a matter of fact you can mix concrete with shovel, buy concrete mixer will come very handy. On my opinion floor should be made out of concrete as it makes cleaning much easier. One of frequently overlooked things is power supply on horse stable site. You may be be of the opinion that a horse stable doesn't need power supply, but in this case you need either power generator or cordless tools during the construction. As a matter of fact cordless drills are available for a long time and these days you can get a cordless circular saw for a reasonable amount of money. One nice tip when buying cordless tools is to buy all your tools from same manufacture and voltage. This way you can use the same battery for cordless drill and circular saw. Well know manufactures like Makita, Hitachi, Milwaukee or DeWalt produce their best cordless drills in two sizes compact drills generally speaking use 12 volts batteries and full sized 18 or 20 volts. This becomes also important when buying cordless circular saw, as circular saws operate on 18 volts. This means, that you can use the same battery for both tools, but you have to pay attention on the voltage even if you are buying all tools from same manufacturer. Also best cordless drill article is a must read before buying your tools.