Because leather is PH neutral, look for a PH neutral cleaner for motorbike leather. You can use a very simple soap but it is really worth buying a product designed for the job. Products designed for car upholstery leather are not always suitable for bike leather, and again don't use saddle soap - although it has been used for years on equestrian equipment, that is veg-tanned leather and very different to chrome-tanned motorbike leather. Vegetable tanned leather tends to be much stronger, and saddle soap contains lye, which is corrosive. Also, saddles should be re-oiled after cleaning ......
You shouldn't oil your bike leathers - by their design you shouldn't let anything through the pigmented coating, so a product like this will just stay on. It will eventually soak through, but you shouldn't try to soften the bike kit - you just need to keep it clean and protect it from moisture.
Hoof oil is another thing you can't use on bike leathers simply because it's a softening agent and it's not designed for this type of leather. Anything containing wax just stays on top of the pigmented leather. Dirt and grit then get trapped inside, which wears away the protective surface of the leather.
Therefore, use a product designed for bicycles and wipe gently with a cloth, or use a soft bristle brush or sponge in a circular motion. Don't scrub it - just gently get the bugs and dirt off; you're just stirring up the dirt. Then, just rinse them off with a sponge slightly soaked in warm water. Finally, you should use an aggressive product designed for motorcycle leathers - use the instructions on the packaging as a guide.
Never use a microfibre cloth - the small fibres that catch the dirt will grab it and wear away the surface coating, causing more damage. Your best bet is inexpensive face wipes - terry towels or similar. Some people use baby wipes and other skin care products, but this is not a good idea as the skin contains natural oils and will regenerate. Not so with leather! Using some of these products is like T-cutting the leather, which opens up the surface and speeds up the degradation process.
Leather should not be soaked, so if your gear has become very dirty, inside and out, you should take them to a professional.