As you know, I have gotten into the gracious hobby of fountain pen use. I fell into this easily as my parents used fountain pens a great deal and I would pick one up as a matter of course. However, you might not have that in your background and no one to ask about which ones to choose first. So, I thought I might offer some help in answering the question of what a good first fountain pen would be.
I think that you would do well to choose a pen which is a smooth writer, with a nib in the width you like in a roller ball or ball point. So, if you naturally gravitate to a wide line, then choose a pen which will offer you a broad nib.
Second, your first pen should be from a good company but not the top-of-the-line expensive. Lots of very good companies make a great introductory pen. Pelikan is one of the world’s top pen makers. They are German and are famous for their wonderful nibs. They make a children’s pen which is just superb, the Pelikan Pelikano JR. It is a bit thick, easy to grasp, has a good sturdy steel nib in medium, and is carried by a variety of pen stores. They come in: blue, green, red, and orange and are about $12. They take cartridges but can be changed to a converter if you want to refill from a bottle ($5 extra). A great value, and a pen you will keep for the rest of your life, too.
The Lamy (pronounced “lah-me”) Safari is another German pen that is a more adult model. They have interchangeable nibs, so if you decide to switch from a fine to a broad, you can. They come in a variety of colors and have a window in the side of the pen so you can monitor how much ink you have left. They can take cartridges or you can get a converter to be able to fill from a bottle of ink, too. This one comes in a lot of colors: green, navy, black, white, red, and yellow. There are a number of different Lamy models and one of those might suit your taste better but you just can’t go wrong with a sturdy good looking Safari for about $36.
Kaweco sounds like a Japanese company but they are also German and they produce a pen which is very small but which is tremendously popular. The Sport model is about $25 and when capped in your pocket is a very trim 4.13″ long, but take off the cap and put it on the end of the barrel (called “posting”) and you have a full sized ready writer that a great many people swear by. The choice of colors is astounding (including a clear demonstrator model). It only used international short cartridges but they are readily available. The nib is gold plated steel and is available in a choice of widths from extra fine to broad. Clips are extra but at $25, it is quite a bargain.
At this point don’t worry about whether to use a cartridge or a converter in your pen. Cartridges are very popular and the “short international” type is pretty universal and easy to get (even at Staples). Later on, if you develop a taste for unusual colors and start exploring, then by all means spring for the extra $5 or so for a converter for your pen which will enable you to refill from a bottle of ink rather than inserting a cartridge.
Just about any paper is good nowadays, I would not worry about fancy papers just yet. Get to know your pen first. Use it every day and learn the feel of a good fountain pen skating across your page. I think your handwriting will be more expressive and your experiments with fountain pens may very well encourage you to write more letters (!) to your friends and relatives and also bring some zest into your daily correspondence.
Enjoy the exploration of the fun world of fountain pens!