Any song that you want to create is going to have some layers to it. While just an acoustic guitar or a piano along with some vocals would be alright for a track or two, it would be extremely difficult for you to end up justifying a situation where you would create an entire album with such a sparse kind of lineup. Adding layers is essential once all has been said and is now out of the way, but being capable of doing all of that yourself would result in things becoming somewhat prohibitively expensive for you.
The reason behind this is that you would be require to buy all of the instruments that would go into the song that you are trying to play, but the thing to note about music production is that the modern age has created a lot of affordable solutions that would help make it cheaper for you to make a song entirely on your own than might have been the case otherwise. One such solution would be a midi controller, and it can help make things cheaper by preventing you from having to buy any of these instruments in the first place.
Instead, you can simply use the midi controller itself to make any and all music that your heart desires. This means that one purchase can put you in a situation where all of the instruments that you want to end up putting into any kind of song at all would be within your reach, and there wouldn’t be anything else that you need to do in that regard at all. You can digitally replicate all kinds of instruments thereby diversifying your repertoire.