There isn't really a tried and true "easy" way of making pony music.
Producing music for a fandom or just in general requires years of experience aswell as personal knowledge on how well you understand music theory, chords, things of that nature. You also require a DAW (digital audio workstation) which appeals to you and fits your style of production. I personally use FL Studio 11 and Reason 5.
I have 5-6 of years experience with music production and 2 years of audio engineering, so feel free to ask me any questions!
Like what ThunderDash said above, a "good sounding vst" won't do anything if you have no experience with it.