Starting out as Disciple of War can be tough. I mostly relied on using Potions. My first character on another server (before I made my current character on Tonberry) was a Lancer. I believe you unlocked Life Surge at Level 10 or so? That was a rather unreliable healing skill I had, but for the purposes of solo content it was fine.
Arcanist is a good class to start with. You get a bit of everything. You get to heal, you get to DPS, you get a tank pet. Later on in dungeons, you can double up as a raiser as well.
When I played Lancer for a bit, I realized how much I liked dungeons and that DPS queue times were too long. So when I made my current character on Tonberry, I decided she was going to be the cutest Lalafell tanker ever. Never looked back. I still love dungeons, even now, so I cringe when I have to level DPS classes.
Also consider that for any class to be useful end game, you need to get the relevant cross-class skills. For example, to get a Summoner, you need Arcanist 30 and Thaumaturge 15. However, to be a really effective Summoner, you will need to level up that Thaumaturge to at least 26 for Swiftcast, because it's such a necessary skill to have for mages. Certain DPS classes like Monk or Bard would have to level a Lancer to 34 for Blood for Blood. In that sense, I find that Gladiator/Paladin is the easiest class to play if you want to fast track it to end-game. This class does not "require" any cross-class skills compared to all the other classes that I know, it can be largely independant and still be really effective. The best cross-class skills a Paladin can have are Stoneskin, Foresight, and Bloodbath. However, they are not mandatory to have, compared to having Swiftcast (THM 26) on a White Mage/Quelling Strikes (ARC 34) on a Black Mage/Blood for Blood (LNC 34) on a Monk or Bard. The only thing is I read earlier you may not want to be a tank, but if you want a class that you don't need to invest too much time in, consider a Gladiator.
While I am not encouraging you to not get any cross-class skills as a Gladiator, I am just saying the class is fairly self-sufficient. Eventually I would still recommend you to get the cross-class skills you need, but for the purposes of end-game, you can go without those skills.