But he was born a normal monkey. He eventually transcended to godhood by becoming immortal an so powerful.
Well, "born" in that he came from a stone egg birthed from a magic stone that sat absorbing the energy of heaven and earth since the beginning of time...
Sun Wukong, or Monkey, was born from a magic stone that sat on the top of a mountain, that had been receiving the powers of the heavens and the earth since the beginning of time and had thereby gained miraculous powers. The stone stood 36 feet and 5 inches representing the degrees of the heavens and 24 feet round representing the division of the solar calender. With nine hole in it for the nine trigrams. The stone developed a magic womb, which burst open one day to produce a stone egg about the size of a ball.
When the wind blew on this egg it turned into a stone monkey, complete with the five senses and four limbs. When the stone monkey had learned to crawl and walk, he bowed to each of the four quarters. As his eyes moved, two beams of golden light shot towards the Pole Star palace and startled the Supreme Heavenly Sage, the Greatly Compassionate Jade Emperor of the Azure Vault of Heaven, who was sitting surrounded by his immortal ministers on his throne in the Hall of Miraculous Mist in the Golden-gated Cloud Palace. When he saw the dazzling golden light he ordered Thousand-mile Eye and Wind-accompanying Ear to open the Southern Gate of Heaven and take a look. The two officers went out through the gate in obedience to the imperial command, and while one observed what was going on the other listened carefully. Soon afterwards they reported back...
So he hardly started as just a normal monkey; he was the condensed energy of the universe that merely took the form of a monkey.
As far as Jingu Bang, it might take some houseruling to get it just right. Impact is a must, it flat-out treats the weapon as 1 size category bigger. Transformative, but instead of the normal function of the ability, it allows it to gain an additional size category over Impact, though he now must wield it in two hands (Staff Mastery makes it 1-h but it's 1 category too big so back to 2-h). So, in instances where he isn't going to use Spell Combat, he can enlarge the staff for more damage and maybe even reach. So, ideally, it would be a +3 Transformative Impact Quarterstaff and I think that would be a pretty good fit for the source material.