"Despite a long search for evidence, nothing has emerged to confirm the Viking-Age ingestion of hallucinogenic mushrooms, the inhalation of narcotics, and so on. There are, however, two archaeological exceptions to this." The Viking Way by Neil Price (The exceptions are seeds of henbane and cannabis found in graves)
Neil Price - The viking way, magic and mind in late iron age scandinavia
There's also a pdf of [The Archaeology of Seiðr: Circumpolar Traditions
in Viking Pre-Christian Religion](https://www.google.com/url?sa=t&source=web&rct=j&url=https://ppg.revistas.uema.br/index.php/brathair/article/download/616/535/1730&ved=2ahUKEwjk0J-4jYH3AhUWRvEDHcx4CrAQFnoECCUQAQ&usg=AOvVaw310LAPqUb4uljzjwJBMuUw) floating around. Nevermind the spanish intro, the text itself is in english.
Neil Price - The Viking Way: Religion and War in Late Iron Age Scandinavia
This is a very good place to start. Oh, and avoid Edred Thorson / Stephen Flowers at all costs.
Buy this book as a starting point. Understanding what we actually know based on historical fact (spoiler: very little) is an important foundation to build upon, if you ask me.
Then check out this book (written by a scholar who is also a practitioner herself).
The Road to Hel is an excellent resource for more context information as well.