Can a lefty safely use a modern fountain pen? I've always stuck to the higher end "mass-market" pens since I end up wearing/smearing the ink of better pens.
I'm a lefty who uses a lamy safari. I'm pretty darn happy with it and use it every day. Also use noodlers heart of darkness ink which is both a lovely vibrant black, and also adheres to the paper but not my hand!
Try a quick-drying ink from Noodler's, such as Bernake Blue or Bernake Black. I'm a big fan of the Platinum Preppy with an o-ring to seal the whole body allowing you to fill it with ink—it's dirt cheap and writes very well. I recently picked up a Pilot Metropolitan, slightly more money but again, impressive value and it comes with a converter (which is like a cartridge that lets you refill with your own ink).
To add to what the others have said, besides writing overhand (so your hand doesn't drag across what you just wrote), look for smaller nibs, drier inks, as well as more absorbent paper. Anything that will make the ink set faster instead of staying on top of the paper.
I'm not sure what the exact problem is with writing left-handed.
I have been switching between writing right-handed arabic and english all my life with every kind of pen available, it has never been a problem. I never even noticed there's a difference.
I have a carbon fibre and silver Caran D'Arche. It cost me GB£ 500 seven years ago, and I use it daily. It, and my watch (a Breitling Navitimer) are the only things I've ever bought where I was able to perfectly balance utility, quality and aesthetics, and hence didn't care less about the cost.
The point is that what works for one person doesn't necessarily work for another.
There are whole networks of fountain pen afficionatos with reviews, writing samples, etc for pens, paper, and inks. It's amazing. However, if you're starting out, I recommend getting a cheap pen and then move up if you feel the need.
The cheap Pilot Varsity disposable ones are a fantastic starter FP, as they cost about $3, a tenth (or less) of the price of a Good Fountain Pen. Ink isn't changeable, but the leaking is minimal. (They aren't waterproof, though.)
The advantage is, if you decide you don't like it, you aren't stuck with it, and if you lose it or loan it out, no big deal. I also like that Staples tends to sell them in a pack of three colors.
I've also used the Bic one [1]. It's also OK, and is partially waterproof, but its cap drives me bonkers. It's been a long time since I used one, though, as the pads at current employer bleed a bit when I used my fountain pens. I liked writing on the sugarcane spiral bound pads from Staples because they were so smooth.
can you go to a stationary store or art supplies that deals in Waterman, Cross, Mont Blanc etc and try a bunch. Mostly they have gold nibs which make the ink flow really nicely, but they all balance and fit your hand differently, and after a while, the nib softens to how you write
Personally I found that it encouraged me to write more.