You can always prayer from anywhere. There is no need for any specific attire, ritual, diet, holy book, temple, synagogue, church or anything material. You are the "temple of God". God resides within each of us.
There is advantage when more people come together to pray. Higher the number of people coming to pray makes the prayer stronger. They do not need to be within a building or church.
However, most the time the congregation in churches are listening to the voice from pulpit. Beware of those messages from the pulpit as they contain hate, contempt and false information about others who don't follow those doctrines or views.