Try
IAMPETH to start with.
Also
The Fountain Pen Network has a number of discussions on improving your handwriting, and the websites and books to help.
You can create and download your own practice papers from
Incompetech
As for the pen, it depends on what sort of handwriting you want to do (Spencerian, Business Script, Italic, etc.)
There are fountain pens with a range of nibs, from round to stub to italic and Naginata Togi and Architectural.
There are modern dip nibs such as the Hunt 513EF for normal writing to the Brause 361b or Leonardt 40 for italic style. I think the Hunt easier to start with.
View attachment 2218723
(Note, as you can see from the scan, I do not do calligraphy, I just write...)
There are also fibre tip pens for Calligraphy, such as those by Artline.
If you are going to use dip nibs, do not get conned into buying expensive "calligraphy" inks. Sheaffer Skrip (blue or black) is good enough. (Also Pelikan 4001 Blue-Black - not Blue, not Black, Blue-Black, it has special features that will help you.)
Learn to develop a "Light Hand", The pen should write with only the weight of the pen on the paper. You should then hold the pen with only enough pressure that the nib writes with just its own weight and perhaps a tiny bit more. Somebody should be able to come behind you and slide the pen from your hand. You should not normally be able to hear the pen writing on the paper. If you can hear "scratching", you are pressing too hard.
Ballpoints are bad because they make you press hard.
Learn the "Tripod Grip
View attachment 2218724 Note the first joint of the index finger is curved outwards. If it is pressed inwards, you are pressing too hard.
For papers Rhodia, Clairefontaine, Oxford are all good enough if you want lined paper.
If you want to print your own, then HP Color Choice 100 or 120 GSM is suitable.
Don't forget, you are practising, not producing saleable artwork, so don't buy expensive inks or expensive "art" paper.
PS, if you are buying a dip pen holder and nibs, buy a straight handle/holder, not an oblique one.