My best advice is to get all your characters equipped with a fair stable of gambit slots, and set nearly all of your gambit slots to white magic. And you're going to want to get *everybody* all the white magic there is to get. All the white/green magic in the game is useful to every character, really, but white especially. You'll want auto-heal gambits for sure, but the percentages are sort of personal preference. You may micromanage them at least a little during tough fights anyway. But yeah, once you get a fair way into the game, you're going to want everyone with all white magic and you'll want at least a few people with a full set of gambits set to just removing status ailments. I basically had the three girls on heal/status duty, with the three guys doing primarily attacking but switching their gambits around in any circumstance that required it. If there were good opportunities for the girls to go apeshit, I'd just manually have them attack or cast aggressive magic.
Anyway, that's the goal I'd work towards. For me, having the status stuff taken care of was a huge load off my mind.
I think what Cobra is thinking of is the Stilshrine of Miriam. There are several really bad dudes guarding something in there that will probably kick your ass when you first get there. I'm not sure what your issue might be with the Tomb of Raithwall, but yeah, leveling a bit never hurt. I never found it necessary to spend *too* much time grinding for levels, but I did occasionally do runs for items to sell in areas where I could rank my chain up super high to get better stuff more quickly. In doing that, I tended to also level a bit.
Sorry I can't be of more help. It's been a long time since I was that far back in the game. If you're getting killed by status stuff, that's something to watch. There are a metric crapton of enemies in the game that can do horrible status stuff to you, etc., and it very much helps to have ways of dealing with that automated and decent stocks of items to deal with it in case you need to have status effects removed quickly (spells take longer) or run out of magic.