MSI B450 Pro Carbon is a good bet, it's usually $130. If you don't need the audio or WIFI/BT and such you can probably get away with B450 Tomahawk.
There's cheaper boards than that but they're usually not worth it, you save ~$20-30 but end up with a worse experience.
For Ram if it's going to be plug and play with a $120 budget I'd look into a set of Gskill RAM with 3200MHz speed CL16 (Cl14 is usually $180-200).
Last edited by AlphaC; 03-01-2019 at 08:30 PM.