Marian reforms

The Marian reforms of 107 BCBCAE were a group of military reforms initiated by Gaius Marius, a statesman and general of the Roman republic.
Roman army before the Marian reforms
Up until the last decade of the 2nd century BC, the eligibility requirements to become a Roman soldier in the service of the Republic were very strict:

He had to be a member of the fifth census class or higher.
He had to own property worth 3,500 sesterces in value.
He had to supply his own armaments.

The last requirement, in particular, produced a division among Roman census classes (distinct from the usual plebian/patrician divide), in which four standardized unit types (based on how much money the soldier could spend on his own arms and armor) comprised each legion:

Velites - The poorest (5th class proletarii) and often the youngest citizens, who could not afford a gladius, a shield, a helmet or
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