When Tyrion first arrives at King's Landing, his only friends are Bronn and a couple of Mountain Men. But he soon earns—by which we mean buys—a couple bros to keep in his corner.
Bronn is a sellsword, an excellent fighter, and the captain of Tyrion's guard, who helps Tyrion bolster the defenses of King's Landing by hiring sellswords to fight for the Lannisters. Bronn speaks plainly and could care less what others think of what he says—mostly because he has the sword skills to turn any debate in his favor.
Although he likes Tyrion, he's also in it for the money. When Tyrion asks him if he would kill an infant at his command without asking any questions, Bronn responds, "I'd ask how much" (9.Tyrion.145). After the Battle of Blackwater, he is knighted.
Tyrion promotes Jacelyn Bywater to Commander of the City Watch after he fires Janos Slynt. Bywater proves a loyal fellow to Tyrion and always speaks "the plain truth" (42.Tyrion.96) to Tyrion regardless of whether he will like it or not.
Pod is Tyrion's squire. A shy, introverted, twelve-year-old boy, he won't look Tyrion in the eye when speaking to him (18.Tyrion.86). Despite this, he's super loyal and courageous as he joins Tyrion in the charge of the King's Gate, even killing Ser Mandon when the knight attempts to murder Tyrion. By the end of the novel, Pod is one of the only people Tyrion can trust (68.Tyrion.54).
These are the leaders of the Mountain clans Tyrion hired in A Game of Thrones. They followed Tyrion to King's Landing as his mafia-style muscle, and they eventually head into the Kingswood to engage Stannis's men in guerrilla warfare.