i understand that cores: “MAME + year” requires certain sets…but I could not get any games to load with core: “MAME”…screen flashes and I’m brought back to main menu… with fb alpha, some games does load and some is stuck at a black screen… any help or suggestion…?
yes, use roms from the right sets for the mame core you’re using 
eg, mame 2003 = 0.78, mame 200 = 0.37b5