Is this combo good for a first gaming PC?

Yes. The 9850X3D handles games well and the board has the slots and memory support most builds need. It is a straightforward starting point if you do not plan heavy overclocking.

Can I overclock the CPU on this board?

The B850 chipset supports memory overclocking and CPU tuning, but the PRIME board's VRM is modest. Mild tuning is fine; sustained all-core overclocks are better on a TUF or ROG board.

Does it support PCIe 5.0 graphics cards and SSDs?

The x16 slot is PCIe 5.0, so current graphics cards run at full speed. Check the M.2 slot's generation before buying a Gen5 SSD, since the listing only confirms one M.2 slot.

What memory should I pair with it?

DDR5 only, on AM5. A 6000 MT/s kit with EXPO profiles is the usual sweet spot for Ryzen 7 chips and keeps the memory controller stable.

The board is micro-ATX, which fits most mid-tower and many small cases. Confirm your case accepts micro-ATX and check clearance for your CPU cooler and graphics card.