Welcome, Josiah! Congratulations on starting your primal voyage.
From what I understand, if you want to gain healthy weight, improve insulin sensitivity, and get all the good hormones flowing in your bloodstream, one of the very best things is lifting weights. You'll find a ton of advice on these forums, but Mark has a great post on the subject here:
How to Gain Weight and Build Muscle | Mark's Daily Apple
Ketosis can be great, and I enjoy it myself, but as for a constant state of ketosis, my understanding is that it's not optimal. The body does rely on carbohydrate for certain things like mucus production and Vitamin C recycling, and it seems reasonable to give your liver a break from gluconeogenesis once in a while. You can read a lot about that here:
Perfect Health Diet » Dangers of Zero-Carb Diets, I: Can There Be a Carbohydrate Deficiency?
Very glad to have you with us. I hope you will stick around and let us know how your journey progresses.