When I first start to learn anything new I am always tempted to go and buy lots of fun things to play with and more often than not they turn out not to be what I need and end up in a box not used. I am going to give suggestions of things that I find useful and necessary and suggestions of where you can get them.
Living in Australia, I try to use Australian suppliers wherever possible, and we are lucky to have 2 good calligraphy equipment suppliers, both based in Melbourne. I am not recommending one over the other, the choice is entirely yours. They are https://www.calligraphysuppliesaustralia.com/ ; and https://www.notjustacard.com/ .
In the UK you have more choice and you can often find calligraphy equipment in high street art supply shops, however there are also specialist shops which sell a broad range of equipment and do a good, reliable, international service, such as https://scribblers.co.uk/ ; https://www.blotspens.co.uk/ ; and https://www.cornelissen.com/.
And in the US, two suppliers which provide reliable, international service are https://www.johnnealbooks.com/ and https://www.paperinkarts.com/
And as far as the basic things like pencils, protractors, erasers and rulers are concerned, you can buy these in any good stationery supply shop near you.