In my last church in South Dakota (cowboy country), a month or so after my wife and I arrived there, I looked around the small, country-church congregation. I saw how the men were dressed, informally, to say the least. Suddenly, I felt very uncomfortable in my suit and tie.
When the leadership and I met for the monthly meeting, I asked if I could shed my tie and suitcoat because of my discomfort. They said, "We don't care whether you wear a tie and suitcoat or not."
The following Sunday, I preached on 1 Samuel 16:7, when God told Samuel to anoint the next king of Israel, whom he thought was Jesse's oldest son, Eliab, as follows, "But the LORD said to Samuel, 'Do not look on his appearance or on the height of his stature, because I have rejected him. For the LORD sees not as man sees: man looks on the outward appearance, but the LORD looks on the heart'" (ESV).
Then, I used my attire as the message's example of more-casual clothes, which the people quickly adjusted to.
God only cares about what's in your heart (genuine repentance and faith), not what you're wearing, when you worship him.