While history states that Celtic women were also soldiers, there hasn’t been a lot of archeological data to support that. The burials of Celtic warriors uncovered are so far only of men. When Julius Ceaser invaded Gaul he wrote that only about 25% of the Celts bore arms. The basic Celtic military gear was a set of spears (one to four). The spears could be nearly 2 meters long with spear heads up to 50 centimeters long. They carried shorter throwing spears and also a large shield. Usually the shield was made of wood and leather but there have been bronze shields found. They also wore trousers, shirts and a mantle or coat. The Celtic noblemen also carried a long sword and wore gold rings around their necks called torcs. The fancier the sword hilt and torc the richer or more well off the noble.
Many Celtic tribes had battle chariots. These chariots were light weight made and pulled by two horses. They were made of iron and were small, no more than four meters long and two meters wide.
Some chariots had metal rings and connectors that were used to strengthen joints and flexible connections. The thing that made Celtic chariots unique was that the platform on which the warrior stood was not fixed but held in suspension which made it a much more comfortable ride. When they drove the chariots into battle there would be two warriors on it. One would jump off and enter the battle while the other one would stay in the chariot, nearby, in case a hasty retreat was needed.
Some of the Celtic tribes had warbands like the Irish Fianna or the Gaesates. Some legendary Celtic names of leaders are Fion Mac Cumhaill or the Two Kings of Gaesates. The Celts fought lots of battles some with a few fighters and some with many tens of thousands. Many historians believed that one of the main reasons the Celts finally lost to the Romans was because they had no real organized military and the disorganization made them vulnerable in battle. When they first went to battle they would let out horrible war cries that frequently upset their opponents, at first, causing them to run in fear. After awhile though, the Romans got used to it and it no longer worked.
Before the battle the Celtic war leaders would parade in front of the troops showing off their battle skills and bad mouthing the enemy. (Sort of reminds me of modern day professional wrestling on TV). Roman historians state that the Celts had little ability to endure prolonged battle. That they weakened easily but that view has been argued against. Modern scholars feel that since Romans viewed endurance as one of the best of Roman virtues then the Celts couldn’t have that same virtue. That is why they said that the Celts were barbarians who gave up easily. Modern scholars refer to the fact that the Celts were not easily defeated after all and that Celtic warriors would fight valiantly til the end, even when they knew the battle was lost. Often the Celts would kill themselves and their families rather than surrendering and being sold into slavery.
Read more about Celtic Warriors in Lords of Battle: The World of the Celtic Warrior (World of the Warrior