Manchester United are reportedly only beginning their summer of splashing the cash following the signing of Memphis Depay from PSV Eindhoven on Thursday, 7 May.
The Dutch international's move was confirmed by both clubs on Thursday, and Louis van Gaal will be delighted with his first capture of the season.
The Dutch forward, who made his debut for the Netherlands team under Louis van Gaal has been impressive for the Eredivisie side this campaign and helped them to the title for the first time in six years.
But, according to the Mirror, this is only the start of United's transfer activity as they look to spend big for the second consecutive season after spending over £150m during last year's summer transfer window.
The Red Devils have been linked to various players, as Van Gaal looks to strengthen his side to be able to challenge Chelsea for the title next season and has identified the positions that need strengthening.
The former Bayern Munich manager has made it a priority to strengthen his defence and forward line after seeing his side struggle at both ends of the pitch during the course of the campaign.
The latter two are available for transfer after the Bundelsiga club admitted that they could be sold if the right offer comes in. Gundogan, who has just one year on his current deal, is likely to leave the club after rejecting their latest contract offer, but Hummels has two years on his deal and could be retained if interested clubs do not match Dortmund's valuation of the player.
Clyne, on the other hand, has indicated that he is happy to remain at St Mary's despite the interest of United, but a bid in the region of £25m could tempt the south coast club to part with the player.