Just go for it. Mimosa and rue is easy to order, so you can always get more later on. 3 gram mimosa might be weak, or it might be strong, depending on the you, the material and your brewing. For me, and my mimosa, 3 gram would be pretty strong.

I would say it is a good dose to start with. Might give you nothing, but then again, the chances of overdosing is much less.