It was not mandatory to read cryptography for dummies if you want to learn cryptography. You just have to go through the basics of networking first , learning networking protocols
Ethernet (Physical/Data Link Layers)
IP and IPX (Network Layer)
TCP and SPX (Transport Layer)
HTTP, FTP, SMTP and DNS (Session/Presentation/Application Layers).
Even if you have read the Cryptography for dummies you can start having a basic knowledge about the working of these networking implementations And after that you should start making your coding skills strong. If you are already good at programming you should start reading
This is one the best courses to learn about cryptography and cryptocurrencies:-http://assets.press.princeton.edu/chapters/s10908.pdf