Yellow cake mix
My family members swear by Betty Crocker cake mix as they tend to produce a much moister cake than other mixes. It also helps if one uses an airbake-type pan.
I have tried the Cake Boss brand cake mixes and they are good. IIRC, Buddy's specialties are yellow and red velvet cakes, so those should be good. However, those mixes are around $4-5, versus $1-2 for Betty Crocker mixes.