I remember the pain that was trying to hit job level 50 with my merchant. I'll tell you what I did:
Stat yourself about evenly in vit and str, let's say 40 in each if you can, and then around 25 dex. Carry ~200 meat, and go south of Einbroch. Kill Metalings. Use the best NPC sword you can get and upgrade it to the highest safe level you can get it. They give decent job experience and good base experience, though it will still take you a couple days for the last 10 job levels (leaf cats in Ayothaya >>> Metalings for job exp but they do have really high flee and attack so if you want to fight them you'd have to re-stat for str & dex and bring lots of healing, plus avoid ghouls and the occasional whisper).
Generally, with the right str stat, you can kill a metaling in 3 hits, doing this:
Mammonite (lv3-4; higher is just a waste of money), Mammonite, normal hit.
They have about 800 HP.
If you happen to have a Cutlass weapon, which lets you use the skill Bash @ level 5, you can do
Bash, Bash, normal hit
instead. The only real advantage here is that it doesn't use money like mammonite does. And I happened to get one randomly from an OVB a long time ago so I used it for my second merchant. I've done both ways, 'cause I have a smith and an alchemist.
Often the metalings won't even hit you that way, and the meat is just for when they do.
Honestly, I used metalings on my thief for a while too until I could handle Toy Factory. They're just a really good way to go from base level 40 to base level 50.
I found this method more survivable than poison spores, and I ended up with 2 metaling cards from it, which I sold for 9.5 million and 7 million respectively (think they go for closer to around 5 million these days though). Selling karvodainilrols from poison spores is a good source of money too though, so kind of take your pick. No guarantees on getting any metaling cards or that anyone will still want them. You also can get a decent source of money from metaling drops, since large jellopies sell for 400z each and flexible tubes & screws aren't too bad either. Just be aware that the map is also littered with thief bugs and (the much worse 'cause it's harder to kill than metalings) porcellios too, both of which loot (so sometimes you can kill five or six things and end up with nothing because the porcellio will come take it all and it takes too many meats to survive killing the porcellio for your stuff).
