I just answered this, but you(?) deleted the question at the same moment. Cut and paste:

On their bodies they most likely used lorica hamata or lorica squamata. hamata was a type of ring mail, with interlocking rings made of iron or bronze (hama means "hook"). squamata was a type of scale mail, with tiny scales of, again, either iron or bronze (or both). A squama is a fish scale. The more famous lorica segmentata, with its overlapping plates, does not seem to come into prevalence until the 1st century CE, though it is possible that examples existed already in Caesar's time (for centurions or tribunes, perhaps). Our earliest secure example of segmentata is from the very end of the 1st century BCE.

Example of a fragment of hamata here Example of a fragment of squamata here

The helmet was standard, made of (again) iron or bronze, called the galea. There were many different variations, but all of them had the basic deign of a domed-type hat with hinged cheek-plates.

The shield was the scutum, made of wood, large, with a metallic boss in the center for bashing. Both ovular and curved-rectangle shapes were possible. Later the square curved type would be standard, but it isn't clear exactly which type Caesar's men used, or if they all used the same. Often times the legions of the Gallic Wars and Civil Wars are depicted as carrying a scutum which is basically rectilinear, but with more curvature than later examples (for instance as here).