I think the best way is to pick which topic you want to study and focus on that such as; Wifi hacking, password cracking, cryptography, web servers, web clients, shells, operating systems, low level hacks and such and such. I think the best way is to learn where your interest lies and then practice and read a lot about that!
Thanks with your suggestions.i decide to go for WiFi hacking is there any site or materials that can help me to start with
There already great tools for WiFi hacking embedded in Kali Linux or you can find them on github. I will say read and practice with them on your local WiFi and see how it works. There are more complicated scenes but just start with basics and read informative books.