The earliest offence Gill pleaded guilty to dates to the same day he left UKIP in 2018.
He continued taking bribes after joining Nigel Farage's new Brexit Party.
Later, he led the party into the 2021 Senedd election after it rebranded as Reform UK.
In mitigation, defence barrister Peter Wright told the court his actions may seem "unfathomable" given the "laudable and noble" features of his political life.
"He recognises, and did by his guilty pleas, the enormity of what he has done and the betrayal of the trust placed in him," Mr Wright said.
Farage has previously said he had no knowledge of Gill's "shameful activities" and condemned them "in every possible way".
Police said there was no link to Farage in their investigation.
Gill also represented North Wales in the Welsh Parliament from 2016 to 2017. Police found no evidence to suggest criminal activity linked to this period.
In addition to the eight charges to which he pleaded guilty, he pleaded not guilty to one charge, of conspiracy to commit bribery.
"Nathan Gill has absolutely been held to account for his activity," said Cdr Murphy.
"That should send a strong message to any elected official or anyone in an official capacity who is asked to act on behalf of another government and paid money to do so."