Explanation:

Shri Gupta is the first Gupta ruler that we know of. He may not have been the first Gupta but we know of him because he left behind a temple built for Chinese Buddhists pilgrims to Bihar. During his time the Guptas were minor kings, and possibly members of the “vaisya” or trading caste (at the time not generally associated with royalty).

Shri Gupta’s son was Ghatotkacha Gupta, who we also know only from inscriptions.

Ghatotkacha’s son was Chandra Gupta (Chandra Gupta I), who would go on to be called the founder of the Gupta dynasty. For a few reasons:

Gupta chronology was taken to start from his date of accession (around 320 AD).
Through marriage, conquest or both, he greatly expanded Gupta territory and authority. He married into the Licchavi family, which was a very distinguished family with hundreds of years of history. He also gained control of much of the rich and fertile Gangetic plain.
He took on the title of Maharajadhiraja (great king of kings) a variation of the title adopted by the great Kushana rulers.
He was the first of the Gupta rulers to feature on coins.
Chandra Gupta I would go on to become the first of the 5 great Gupta emperors.