Stephen So was earlier found guilty by a High Court jury of conspiracy to murder and conspiracy to possess firearms and ammunition without a licence.
The court had heard that So instructed a woman he met online, Chak Wing-sze, to kill a man over an alleged money dispute.
So and Chak met on social media in 2016 in connection with the purchase of war games equipment.
In December 2018, So told Chak to look after three pistols and some 500 live rounds for him as part of the murder plot.
But the plan never came to fruition as the pair were arrested by the police.
In sentencing, Judge Susana D’Almada Remedios said So had taken advantage of Chak’s innocence and adoration for him as he plotted the attack.
The High Court judge also praised the police for preventing the murder.
Earlier, Chak pleaded guilty to two counts of possessing firearms and ammunition without a licence, and she testified against So.
On Wednesday, Chak was given six-and-a-half years in prison.