Start with the Lamy or Pelikan pens that are mandatory in German schools. They have very stiff nibs which won't break if you apply the same pressure you're used to with a byro/ball point or pencil. You can get them in the US. There are fun ones made of wood with brightly colored caps and ends.

Once you are used to them you can use a more expensive (or cheapo) pen with a softer nib. That well let you write both more clearly and much much faster.

Note that a lot of fancy fountain pens are (IMHO) way too heavy and clunky for everyday writing.

I can take notes with a fountain pen way faster than with a byro and the resulting ones are more legible (I have dreadful handwriting). Also I can write this way for hours without cramping which I can't say about a byro since those require more pressure and use push strokes.

If I don't have a fountain pen I have some Stabilo gel pens that are the least crappy alternative. The fountain pen is pretty well adapted to handwriting. I prefer to type but there are many cases where that is an inferior option.

A $25 Lamy Safari has done well for me for the last 4 years.