Born on 9 April 1928 in Rhyl, to an Iraqi Jewish Father, and an Irish Roman Catholic mother, Gubay began his Business career in North Wales selling non-sugar sweets during post-World War II confectionery rationing. When rationing came to an end in the mid-1950s, the confectionery Business ran into difficulties and Gubay moved into Retailing via market stalls.

Gubay founded Value Foods on 11 May 1959 in Prestatyn, and rented its first Retail shop in Rhyl in July 1959. His aggressive price cutting resulted in some manufacturers refusing to supply him.

In 1964 Gubay visited the United States with fellow Director Ken Nicholson, and learnt about the "baby shark" method of Retailing. Combined with ideas gained from West German retailer Aldi, the Business model was based on buying goods on favourable (net 60 or 90) payment terms, distributing and selling them at or below cost before the payment fell due, and using the interest on the resulting cash flow to fund the Business. The first Kwik Save Discount branded store opened in Prestatyn in 1965, and produced more sales than the existing Value Foods supermarkets. The second opened in Colwyn Bay, and by 1970 Kwik Save Discount had 24 stores.

Just before it was floated on to the London Stock Exchange in November 1970, the company changed its name formally to Kwik Save Discount Group Ltd. In 1973, Gubay sold Kwik Save for £14M/$28 million.

Gubay and his second wife lived in Santon, Isle of Man since 1971. He had two children with his first wife, and was petitioned to stay on the island by locals after threatening to leave for Switzerland as a result of a dispute over taxes.

In the 1980s, Gubay paid for a replacement church at the site of St Anthony's in Onchan, Isle of Man. The church was designed by Clayton/Massey, with local Architect John Cryer responsible for the interior, and Gubay's suggestion of a window illustrating Christ walking on Douglas Bay by Chris Spittall as a focal point. In 1990, Gubay paid for an extension to Our Lady of the Nativity church in Leixlip, County Kildare, in memory of his mother, Mary Clarke, a native of the area.

In summer 1997, Gubay told an RTÉ television documentary that he had made a "50-50" deal with God, promising when he was younger and penniless to give half his estate to the Roman Catholic Church, if he succeeded in becoming a millionaire.

Gubay had since moved his focus to property development, via Portville. He has mass Investments, mainly in the United Kingdom, Ireland, and Russia. He was named the top property developer in Wales in 2005.

While recovering from a back injury, Gubay founded fitness chain Total Fitness. In July 2007, Gubay sold the chain, based mainly in North West England and Ireland, with 21 locations and 150,000 members, to the private equity arm of Legal & General, for £70 million.

In March 2010 Gubay announced that he was to transfer £470 million of his £480 million personal fortune to a charitable trust. Half the income must be spent on projects connected with the Catholic Church with the rest distributed at the discretion of the trustees.

On 23 February 2011, Gubay was invested as Knight Commander with Star of the Order of St. Gregory the Great (KC*SG) by the Archbishop of Westminster, Vincent Nichols. Gubay was honoured with this Papal knighthood for his conspicuous Service to the Church and society.

Gubay died aged 87, following a short illness, at his home in Wilmslow, Cheshire, on 5 January 2016.