Despite his assassination, Julius Caesar was one of the Roman Empire's most successful leaders. He was a skilled military leader and was able to conquer Gaul (or modern-day France) over a series of wars from 55 to 50 BC. This allowed him to extend Rome's borders further into what is now France, Belgium, Spain, England, and Germany.
In Rome, Caesar was a skilled political reformer as well as an orator. He was able to regulate Rome's debt crisis to prevent overspending while still providing aid to military veterans and the poor. He also took steps to prevent financial hoarding and forbade any one person to hold an excessive amount of money at one time. His aim was to prevent corruption in Rome and, as its sole leader, create a more centralized and fair government. While this wasn't popular with many Roman politicians, it did cut back on the political corruption that had run rampant in Rome.
Additionally, he contributed to the establishment of the Julian calendar, which was a precedent of the Gregorian calendar that is still in use today. While the previous Roman calendar only recorded 355 days, the Julian calendar recognized the full 365 days and more closely followed the Earth's revolution around the sun.