For a Ryzen 5 2600 and 390x computer. Below are 4 popular motherboards and found parts on Amazon that are on compatibility lists for the motherboards. The budget should be under $420 for motherboard/ram/ssd, but under $400 is ideal. You can also recommend a case cause might get a new one if I leave room for one. Mostly after a stable system that will work great and have zero issues functioning.
Asus Build: $415
Asus Strix X470-F + Trident Z 16gb 3000 + WD Black 250gb M.2 2280
Options: Asus Strix B450-F (reduced total $365)
Gigabyte Build $368
Gigabyte X470 Aorus Ultra + Trident Z 16gb 3000 + WD Blue 500gb M.2 2280
Options Gigabyte B450 Aorus Elite (reduced total $350)
OR
With any 4 of those motherboards recommend RAM and SSD that is in compatibility list.
Asus Compatibility List
Gigabyte Compatibility List
Asus Build: $415
Asus Strix X470-F + Trident Z 16gb 3000 + WD Black 250gb M.2 2280
Options: Asus Strix B450-F (reduced total $365)
Gigabyte Build $368
Gigabyte X470 Aorus Ultra + Trident Z 16gb 3000 + WD Blue 500gb M.2 2280
Options Gigabyte B450 Aorus Elite (reduced total $350)
OR
With any 4 of those motherboards recommend RAM and SSD that is in compatibility list.
Asus Compatibility List
Gigabyte Compatibility List