Whatever job you're interested in is the job you should play particularly when you're first starting out.
You will be leveling with trusts now, so party composition or invites will be a non issue. Melee jobs probably have an easier time getting up and going over a mage job as leveling will be faster and you don't need to worry about buying spells or anything.
Endgame you will probably have a tough time getting into a group as a fresh 119 anything, but WHM and GEO are fairly easy to gear up low man or solo and every group is looking for them, particularly WHM. This is also server dependent, so your experience may vary but these are the jobs you can get into a group on to then gear up your other jobs.
Once you have one 119 job, you can use trusts to get through story content fairly easily and expand out from there trying different jobs to find what you like.
Edit: Here is a step by step guide on starting out and things to work on:
https://www.bg-wiki.com/bg/Quickstart_1-119_Guide