pls advise for applyining visa if you need letter of Invitation from China?

The invitation letter is needed for most of all the application. You may go there for an exchange tour, right?
If so, the invitation letter is needed.

For the group one, it is usually for tourists with at least 5 people and the tour should be organized by certain tour agency. The people in the group are required to enter and exit together, so it is a little bit inconvenient. You are suggested to apply seperately.