I sneak nut flours into everything I bake, so every time I make gluten free pancakes and waffles, I add 1/4 - 1/2 Cup of nut flour for every cup of rice. I grind my own nuts (much cheaper).

An easy ratio is
1 C rice (brown or white or blended)
1/2 C nut flour of choice
1/4 C tapioca starch

Or if you use pre mixes like Gifts of Nature, just add the nut flour 1/4 - 1/2 C to each cup of mix.

Also, we use a ton of Thai Kitchen coconut milk! It is great for gluten free baking. So, for example, if I was making pancakes with that flour amount above, I would also mix in
1/2 Cup of coconut milk
1/2 Cup of rice milk
1-2 Eggs
1 tsp baking powder
no sweetener
AND
2 Tablespoons of Oil

By sneaking coconut and nut flours into things, we are getting that extra fat where we need it, and it makes our breakfast meals much more sustaining!
When cooking Bobs gluten free hot cereal, I always add plenty of coconut milk to make it creamy. Coconut goes everywhere in this house!

And cookies we make are half nut flour to half regular GF flour.

I have recipes for all of this online too, if you want to see what we eat.

My mom had been really struggling with gaining weight, but in her case, she wasn't taking in anywhere near enough calories! She was getting thinner and thinner, so she had to make herself eat more. And she eats snacks like Lara Bars (which are nuts and fruit) and she uses a lot of those nuts, avocados, and natural oils, etc. Nut butters too.
You can type in a days worth of food into Fitday.com and see if you are getting enough calories. If you are way under, like my mom, you may need to ramp up the quantity of foods you're eating too!

Good luck!