In addition to timing things according to when they need to be done, I'd suggest ranking them by their importance to you. For example, you can get relatively inexpensive invitations, and most people throw the invitations out pretty quickly
after getting them. Thus, you might decide that while you'd like to make your own invitations, it isn't of huge importance. In that case, you might decide to focus first on something that either saved you a lot of money or was
of personal importance to you, and do the invitations yourself only if you had time left over. Conversely, if personalized invitations are important to you, you might do them first and leave other things until later.
I ended up with a huge number of DIY projects by the end. However, because I ranked them in order of importance, I never stressed about them. I knew that if I ran out of time, it would only be for those projects of the least
importance to me.