Short answer: we don't know exactly.
Long answer:
Roman legionaries in the very late republican era most likely still used the same type of shield that we find depicted on the Aemilius Paulus monument and that may well be represented by the now lost, inadequately published) Fayum scutum. They certainly used something much like it, which would be a very solid, plywood construction shield about 120cm in height and 60 cm across, curved in the vertical axis, but not dished. It was held by a central, horizontal griup without auxiliary fixtures and probably already had a metal boss, though some may have retained the wooden spina of earlier designs. This is their primary weapon, held with the left arm extended downward and used agrressively. It is heavy for a shield and takes considerable training, but damn it hurts.
Their first attack weapon was a sword, very likely of what we call the Delos type, though older models and even not traditionally Roman ones may have been in use. This weapon had a very roughlöy leaf-shaped, double-edged blade tapering to a point and a wooden hilt with a large, bulbous pommel and guard. The later Mainz type - characterised by more weight forward in the blade, a stronger stabbing point and metal plates on the sheath, though those may be an artifact of survival bias - may already have been in use.
They also carried daggers, though probably not yet of the elaborately constructed "typically roman" type we find later.
Their ranged weapon was a hreavy javelin, the pikum, which at that time may have come oin many varieties. some authorities say the soldiers carried a heavy and a light one, and archeologiusts have tried to identify both versions, but it is equally possible that there were simply different pila around. THe "typical" pilum consists of a relatively short wooden shaft topped by a large, pyramid-trunk shaped protrusion into which a long iron shank tipped with a thin, square-sectioned hardened point was fitted. There were also pilum points that had sockets, so they were likely fitted on plain shafts without the protrusion. Some believe that leaden balls were attached at the bottom of the shank to increase mass. Pila are a bitch to throw accurately, but if you hit someone, you get their attention.
Helmets were most likely the fairly simple-looking but technologically quite demanding Coolus or "jockey cap" type, a copper alloy bowl with a short neckguard and cheekpieces. Other types may well have been in use alongside. At that date, I would expect to still see pilos and Boeotian helmets.
Armour varied, though at this point mail was becoming commonplace, some soldiers may have lacked it. Caesar reports that later in his career, he purchased decorated armour and weapoins for his troops, so I would expect a Caesarian legionary of the civil wars to be armoured with mail and have a fine helmet and a decorated Delos or Mainz type gladius. The "typically Roman" segmented armour may already have existed - finds keep pushing the date earlier - but was not yet in common use. The Typical roman mail shirt was hip-length and had short or no sleeves, but a round or square doubling over the shoulders that was held together in front with a distinctive bronze hook (we often find those).
Greaves and arm protection may have been more common than we think, but we don't have good evidence on those at that date.