Widely considered as one of the most visionary football minds of the 21st century, Pep Guardiola has enjoyed an illustrious time at Manchester City. The former Barcelona player and head coach revolutionised the way the Cityzens approach the game and has stamped his authority on the league.Guardiola's first season was one of the worst of the Catalan's career, and it was clear that his squad needed more work in the transfer window. When that eventually happened in his second summer, both him and the club reaped the rewards.Guardiola has enjoyed immense success at CityIn the 2017/18 and 2018/19 seasons, his fearless City side accumulated a staggering 198 points and won the title in both seasons. Overall, City have racked up eight domestic trophies, the most of any club in this period, and completed the first and only English treble ever recorded. It is worth mentioning that all of this was done with a breathtaking and expansive style of football as well.Despite his stuttering 2019/20 season, Guardiola remains a successful manager in England. The jury's still out on his European endeavours with the Cityzens, which has been the 49-year-old's Achilles heel. In total, Guardiola has overseen an expenditure of €781,408,181 during his time at the helm of Manchester City.Here, we take a look at five of his best signings at the Etihad Stadium.#5 Riyad Mahrez | Leicester City | €67.8mThe mercurial Algerian has been a massive hit at CityManchester City have always had an enviable depth in all areas of the pitch. When they completed the €67.8m signing of Riyad Mahrez, he was expected to one of the players that Guardiola could call upon should he wish to — and not an outright starter. He had only a bit-part role to play in his debut season, starting 14 league games and came on as a sub in 13 games.However, he was relied upon more in the recently-concluded season, and his performances have virtually ensured his place in the team. The mercurial Man City winger registered 11 goals and nine assists in 33 games, starting 21 of those.20+ - Riyad Mahrez has 21 goals and 22 assists in all club competitions since the start of last season - he is the only Premier League player have scored both scored and assisted over 20 goals over this period. Visionary. pic.twitter.com/1IMmQBUoHD— OptaJoe (@OptaJoe) January 12, 2020Mahrez has truly provided City with a cutting edge in attack, and his breathtaking dribbling ability on the ball has been a joy to watch.Overall, he's played just over 90 games for the Cityzens, scoring 25 and assisting 28. With Leroy Sane having departed Manchester as well, the two-time Premier League winner has had more opportunities to display his sublime talent.#4 Kyle Walker | Tottenham Hotspur | €52.70mWalker has been an ever-present figure in City's backlineManchester City's then-record €52.70m acquisition of Kyle Walker was met with much criticism at the time. The Englishman was part of a host of full-back recruits, further highlighting the importance of wide defenders for Guardiola. Out of all the full-backs he's spent money on, though, Walker certainly has been the most successful one.The 30-year-old has started over 30 games in his first two seasons at the Etihad, and an impressive 28 this year despite a few injury concerns late on into the campaign. Widely used as an inverted full-back by Guardiola, Walker has adapted to his philosophy superbly and is one of the best right-backs in the league.Just look at *that* goal-line clearance from Kyle Walker. 😱 pic.twitter.com/zvJLXv3pB0— Squawka News (@SquawkaNews) August 4, 2019He's brought an endless amount of physicality to a shaky defence, and has displayed his fiery recovery pace on numerous occasions.Walker will continue to be his manager's go-to right-back, with his backup Joao Cancelo in talks to leave the Etihad. All in all, he has repaid his club and manager's faith in him. He has been crucial for City's domestic success in recent times.Also read: Top 10 U-21 English talents in football | Premier League 2019-20