Do you always wear hakama and keikogi for solo practice?
How about the bogu? Do you put it on even when there is no one else?
Answer: It is always a good idea to wear keikogi and hakama when you train. I allow beginners to train without keikogi and hakama for a while but I tell them to get keikogi and hakama if they are serious about doing kendo.
Bogu is not necessary if you do not have anyone who strikes you. (my personal opinion)