James Constable set the ball rolling for the U's in the sixth minute as he latched onto Asa Hall's fine cross from the right and powered a header back across goal and home.
And eight minutes from time, Deane Smalley, on as a substitute, put the result beyond doubt from the penalty spot after he was hauled down by Dons defender Rhys Weston.
Ardley said: "I am not going to go looking for excuses but it happens too often that we concede the first goal and that coincides with a six-game winless run.
"We were all right in general play and we work hard for each other but we have been lacking a little bit and we are chasing games and leaving gaps.
"I don't want us to be chasing games - I would rather we were getting the first goal in these games instead. But there is no magic formula to get the boys' confidence up.
"It is tough at the moment but I have to sit down with them and make sure everyone is singing from the same hymn sheet. After that it is just hard work.
"These are my players who I have signed and I have got to lead them. I can't batter them as they have given me a shift and tried their socks off against a strong Oxford side."