I would personally recommend playing 2. Nf3 because it requires an immediate response from black. Nc3 and Bc4 give black a little bit of wiggle room and don't fight as much for an advantage as Nf3 does. I also don't think you can be playing only one opening, because your opponent can play so many ways. But for starters I would recommend checking out the italian game, ruy lopez, and the scotch game or gambit depending on how spicy you want to play.
Hope this helps/if you have any other questions go for it
Some of the observations I have are:
1) Nf3 and Nc3 moves control or attack more of the center of the board than the Bc4 move
2) Nf3 and Nc3 moves help develop the Rooks a little giving them a bit of space
3) Nf3 impacts the center more than Nc3
4) Bc4 attacks a space around the K
5) I’ve seen the guidance “knights before bishops”
Does it just come down to something like play what you know, pick one option to learn further variations first, and go with it, or are there other factors?
Thanks,
dgoldsmith