Monitor: look up threads here on LCD versus CRT, that sort of thing. Or, you could simply by a decent LCD TV (not PC monitor), like this element 32" I have here for $150. (Later on, you can look into a 4k TV - higher resolution means better results when using shaders, see below - wherein you'll certainly need a high-end card.)
You want old-school display experience, use current MAME, and try out HLSL. When you're used to that, explore BGFX and shaders. Lots of threads recently on these things; also keep up with future threads.
See how your system performs. If you don't get full frame rate on the games you like most, look into a card. Buy the costliest you can afford.
Roms go in roms - unless you want them somewhere else. Learn how mame.ini works. Bios, same. This is all in the MAME docs.
I don't play Daytona.
Scifi frauds. SF illuminates.
Culture General Contact Unit (Eccentric)