The Messenger Oracle works well with druid and shamanic Tarot cards
Its deceptively simple but I think its best to really think about which decks your using and why to make this both easy and useful. Although I'm all for intuition I think its important that brain is also plugged in, especially if your reading for someone else who needs your guidance in their life. Consider how the decks your combining will compliment eachother or add more detail in certain areas that is needed.
Working with multiple card decks is a great way to add layers of detail and more depth to Oracle Card readings. You can combine Tarot with Oracle cards to have both detail and personal spiritual messages. There are many ways you can go with this. You can also use another deck simply to supply an extra bit of guidance or clarity at the end of readings by drawing one more card to finish your reading. See each deck as having its own facet or perspective on the situation in question, you will also be surprised how often the cards correlate from different decks.
When reading this way using a method I've seen used by Doreen Virtue all you need to do is shuffle your cards thinking of your question and lay them out, three in a row, face down. Then do the same with your second deck placing your three cards in the same order below the first three card spread, again facing down.
Next turn the first card over from both deck's row of cards. You now have two different cards to interpret, you can see how they may relate to each other or show deeper levels of information, sometimes the two cards combine and form a joint meaning. Go with your intuition here. You then repeat for the next two cards until your done. Please try this exercise for yourself.
You can continue to add rows of cards from different decks but try not t over do it in the beginning. Another way to do this is do a card spread and then choose just one card from another deck to supplement your reading. This could add more light on the outcome or offer further guidance. Another easy way to combine decks is to choose a theme, pick a themed Tarot deck and combine it with the same theme of Oracle cards. For example an Angel themed Tarot deck with an Angel Oracle card deck or a Fairy Tarot deck with a Fairy Oracle. These should work well together.
Dame Darcy's Mermaid Tarot works well with Mermaid Oracle cards
Here are some of my recommendations for complimentary decks. Please add your suggestions below in the comments if you have any other combinations that you like to work with.
Tarot Cards + Archangel Michael Oracle Cards
For empowerment during readings about difficult situations or where the client lacks self confidence.
Tarot Cards + Angel Answers Oracle Cards
Use Angel Answers to clarrify inconclusive Tarot readings or answer additional questions put to you about the reading without doing more spreads.
Tarot Cards + Indigo Angel Oracle Cards
Readings for those who identify with Indigo. Adds more support for the emotinal side of Indigos.
Archangel Oracle Cards + any Power Animal Oracle
An additional card from a power animal oracle can be used to add guidence to what qualiuties they need to embody at this time.
Wisdom of Avalon Oracle Cards + The Messenger Oracle
These decks have a similar vibe but with different voices.
Past Life Oracle Cards + Tarot Cards
The Tarot can give more detail on the past life being explored.
Gods & Titans Oracle Cards + Goddesses & Sirens Oracle Cards
Provides the yin and yang perspective on a situation.
Ascended Masters Oracle Cards + Goddess Guidance Oracle Cards
Similar to the above. Provides the yin and yang perspective on a situation.
Original Video by Doreen Virtue on how she reads with multiple Oracle Card decks: