PS: if you want to get into calligraphy, especially either with flex writing, or block lettering (italics, stubs etc) look into dip pens, such as nib holders, and the loose nibs intended to be dipped, they're typically steel that's not stainless, so will need to be replaced eventually, but they have a variety of points, and require a bit of practice to get just right. You can get a box of cheap Zebra-G nibs which often sold for manga artists, because they flex a lot more than any fountain pen you may find (but still stiff compared to some good dip nibs) or you can get a set of old speedballs or sheaffer calligraphy sets that don't flex but offer a range of different thicknesses on the downstroke (and thin strokes going across) that gives that line variation look that people associate with calligraphy or gothic lettering.
The Pilot Parallel set is a fun means of doing the latter as the whole set is around $35, and they have nib sizes that go way up to 6mm thick, the cartridges made specifically for that model can be blended safely between colors to cause interesting visual effects while writing.
I usually say I never spent more than $200 for a pen, anything of higher retail value I typically managed to get in barter or trade-ups from fixing old vintage pens, selling or trading them.
Really depends on the pen, for example that Jinhao 159, a huge brass Chinese monster can be had for under $5 thru various sources like eBay but the Goulet branded nib in it runs about $15 (still a steel nib, but a tad better quality than the one Jinhao ships with).
Likewise you can go much lighterweight with a good nib out of the box with either a Pilot (Japanese) Petit1 for $3 (cartridge only), Platinum (Japanese) Preppy for $5~ (cartridge/converter/eyedropper, but can be known for cap lip cracking if posted), Pilot 78G for around $10-12 (includes a squeeze converter and more nib options), or Pilot Metropolitan/MR for around $15 to $18 (aluminum, sleek, has a snap cap instead of a screw cap, and comes with the same con-20 style squeeze converter as the 78G).
Some of the German options are a little more expensive and often cartridge only (or don't include a converter on the cheap end) such as Kaweco Sports, Lamy Safari around the $20-30 range, and Lamy Al-Star, Faber-Castell Loom and Basic getting into the 40$ range.
My personal preference is usually if you're looking under $20 definitely go for either a Pilot Metropolitan or 78G, probably a medium size nib starting out (A Japanese (Pilot, Sailor, Platinum) is about the same as a western fine [lamy, fc, sheaffer, parker, waterman, etc]) , but if you want it under $5 consider Pilot Petit1 (cartridge only) or Varsity (disposable with a barrel pre-filled with ink), or the Platinum Preppy (three different nib sizes available, and can use cartridges, converters for bottled ink, or can have the barrel filled with the help of some silicon grease on the threads and an o-ring to prevent leakage).
But once I look at between $20 and $80~100 I'm looking at vintage pens with 14K gold nibs (gold doesn't mean it flexes, or is any softer or smoother, but given the age of most vintage pen, gold will not corrode/rust, so can be cleaned and still have no rusting damage as long as the nib hasn't been bent, so a good non-bent or tip-less nib that's blackened can be ultrasonic cleaned to get all the tarnish off and still able to write good as new, old vintage steel nibs may have pitting or rust underneath). Notable favorites being Eversharp Skyline standard, Sheaffer Touchdowns and Snorkels, Parker Vacumatics, Parker 45 [mostly steel nibs under $50], and in some cases Parker 51 Aeromatics. You can often get old Esterbrook pens with new-old-stock steel nibs as those were a popular brand that can screw in and out to replace nib units something most other brands didn't do, and some of the old Esterbrook Js were relatively easy to re-sac and restore.
Above $80-ish there are still some notable vintages I like, but then you get into some good Modern pens that often go on sale, such as buying a Platinum Century #3776 with a 14K gold nib with a variety of nib offerings for around $80 to $100 from Japan (usually thru Japanese eBay sellers or Rakuten), similar deals with Pilot Custom 74, and Sailor Pro Gear Slim (formerly Sapporo) and some instances of the smaller 1911M ("Profit Standard", versus the larger 1911L called a "Profit 21" that comes with a 21K gold nib). But what's nice about the Platinum Century 3776 is there's the option of a 14K "Soft Fine" nib, similar to the Pilot Custom 74 option of Soft Fine, or Soft Fine Medium (I really like the Fine-Medium width in Japanese sizing).
Beyond the $100 range is really going to depend on personal preference, for example one of my favorite vintage pens with a very large ink capacity is a 1956 Pelikan 400NN, holds easily 2.0ml of ink (most hold less than 1ml, and even the modern huge Pelikan M1000 holds 1.5ml), is smaller and slim, but long enough to hold well in larger hands, and often had a softer springier nib (usually semi-flex at best, but shouldn't be expected to produce anything more than minor flair), and those can be found between 150-200 , which is a few hundred dollars cheaper than the firmer modern Pelikans. Though you can interestingly enough buy the modern M200 with steel nibs from Japanese sellers for about 100 (half the price in most other markets).
So there's a huge range of offerings especially when you factor in restored vintages, and the options and opportunities become endless when you consider there are over a thousand different kinds of liquid inks specifically made for fountain pens (never use India Ink, or inks intended only for dip pens in a fountain pen, as they may be destroyed). Everything from bright vivid colors, washable inks, permanent inks, inks that sheen different colors on richer paper, or have a bit of shimmer to it, or fade from dark to light varying with the wetness of the nib. And over time if you develop a light hand you can write longer and experiment with a whole variety of pen, nib, ink, and paper combinations until you find one that's just perfect for you.