Before beginning any Sadhana, adopting a Guru will only make the practice more conducive. However, in the absence of a Guru, you can still perform Sadhana of the God or Goddess name and certain Stotras. Since you are reading this book, you will also learn what can be done in the absence of a Guru and how you can symbolically accept someone as a Guru to complete your practices i.e. sadhanas on your own. This book explains it all.