Before you worry about the jobs you have to level and the subjob you need, just take a moment to think about whether you can invest enough time/effort to get a harp for 3-4 songs and a Relic horn from Dynamis. Without one or both of those special pieces of gear, which require a great deal of time and will most definitely lead to a lot of frustration, you will NEVER get an invite to relevant content. Others may sugar coat it for you, but that is the truth no matter how unfortunate it is. This game is full of elitists, and you will not be invited to do anything without 3 songs at the least. Just ask all those paladins who don't have Aegis/Ochain (special shields).

Since you mentioned you don't know people in the game to do things with, it may be worthwhile to think about playing another job that requires much less work, like GEO, COR, or WHM. I hope I don't sound mean saying this. This game needs more bards, but the playerbase is very unforgiving towards them, so be prepared.