I think people over-complicate fountain pens a lot. I have a Lamy Safari that I got in 2012 and works just as well today. It's what I still recommend to anyone who asks what to get. Just get the pen, with its cartridge, add more cartridges -- you can stay here and already you're way better than with most standard ball pens that you'd be using otherwise. Then, get the small converter, plop it in, get your first bottle…
I think this kinda misses the point of what lost modern pen enthusiasts are looking for. For one thing, limiting yourself to pre-filled cartridges locks you out of 95%+ of the fancy ink out there, which is sold bottled for use with internal reservoirs.
Yeah, Waterman is not that "fancy", but being able to carry 8 long cartridges of Serenity/Florida blue with a dependable pen is hard to beat if you are on the go.