I have 13 sp into Final Attack. I did not hear about it being bad until I put that much sp into it. Would it be better to buy 13 sp resets or just go ahead and max it? (If it isn't going to hurt me too much, I would rather leave it, but I don't want something that will really hurt me.
Final Attack for what class? If you're still a 2nd job, you're better off making a new character and saving that NX for Gachapon, AP Resets or Teleport Rocks.
Not everyone likes to remake their character, and its not a big deal to just use your NX for a short while on resetting it out while you make money in other ways. Might be the most "money efficient" but remaking a char can be quite annoying.
Getting final attack means you can't go hybrid. Not going hybrid means you either have a shitty 3rd job (pure spear) or you can't boss in 4th (pure PA). Maxing it would be very poor idea, unless you're intending to leech until 4th job.