Since this instance is very new there isn't a lot of data cached on our server. As more of you join and add your own subscriptions to the community, we are being rate limited by other instances. This is a natural part of how federating works currently and it will sort itself out. Growing pains.

Depending on the communities being joined it can take anywhere from a few minutes to hours or even a day or so to smooth back out. It isn't anything to worry about, join whatever you feel like and the servers can sort it out. There isn't anything we can do about it.