None of us here knows, and perhaps at this time even your wife doesn't know. My advice is for you to enjoy the adventure that you and your wife are starting together, beginning with looking at different types of dildos, talking about them, and letting her decide which ones to purchase. She may be interested in more than one, including a vibrator.
Then let her show you how she wants to use it. Be very sensitive to what she likes, doesn't like, and new ideas that she has. A small step would be asking for her to switch it around - suck the dildo while your cock is in her pussy. Encourage her to tell you her fantasies, like whose cock she wishes the dildo is.
Let her be the leader, don't criticize her, and enjoy the journey.