So i really want to start playing an instrument but cant really afford to buy a piano or take lessons. Do you think its possible just to buy a keyboard and learn from a book? ANd if so what type of keybrd is good for begginers ?
thanks 
Of course you can. Many people do just that. I learn by my-self with just a keyboard and internet. And know I am a real pro.
First, you need to learn the basic scales and chords.
The right technique to learn piano depends in your expectations. If you want to be an excellent pianist with classical music, learning by yourself is not a good idea. If you just want to play some rock, pop or ballad songs, learning the chords will be enough to start.
In this web sites are all the chords. Start with learning all the major and minor chords.
http://www.nfo.net/MFILE/
http://www.8notes.com/piano_chord_chart/
Choose any song you want to learn (example: Coldplay