Where are you located? See if you can get Victor nearby, they have grain inclusive and grain free foods and is very reasonable on price. Victor Super Premium Dog Food
If I had to agree with anything from 3Toes list, I'd say look for Fromm (Gold and Classic lines), Whole Earth Farms, First Mate (Classic line) or Annamaet. (Original line) They're good foods that aren't going to break the bank. A lot of people like Diamond Naturals, 4Health and Kirkland Signature and they're very reasonable in price as well but they're Diamond products so you'll have some people who are iffy about it and others who've never had a problem and are happy with it.
Some raw each day or a couple times a week would be a great addition to any kibble! Beef, turkey, lamb, chicken, pork, fish, venison, ect. You could get some ground foods and give a meatball sized chunk or two each day/couple times a week. Or cut up some chunks of whole meats into a couple ounces to offer. Raw eggs are good additions. Canned salmon, mackeral and sardines packed in water are a favorite among dogs and good for offering omega-3's into the dogs diet which help keep the skin, coat and body in general healthy. Raw meaty bones would be good for added nutrition and keeping the teeth clean. You can also look into Satin Balls while putting weight on her which are based around raw beef with some other ingredients. They're made specifically for weight gain and will do it pretty darn fast so be mindful of feeding them. Here are links to two different ones, though they're roughly the same thing...
Holistic Dog - Satinballs Satin Balls
Satin Balls Original Recipe. Includes Substitutions for key ingredients for when you do not have everything you need. Heartland Great Dane Rescue, Inc.
Either one you can add or remove the egg shells. The first calls for just the yolk but I'd add the white AND yolk personally.
For joint health, try making a bone broth. My pups LOVE it! It gives them extra fluids, it's packed full of nutrition and also has natural "joint supplements" already in it!
Homemade Bone Broth or Stock: Tutorial | Wellness Mama
I'll just link that one tutorial, you can Google 'Bone Broth' for more information than one could ever want/need about it. Lol! You don't have to add the veggies either, you can JUST cook the bones if you want to. I drink it too so sometimes I add dog safe veggies, sometimes I don't. I also use the bones plain, I don't pull them from roasted animals and things though some people do cook the bones some in the oven before boiling them. I don't, I just toss them in raw.
Otherwise you can get joint supplements from the store, which yes many people like to give even if the dog doesn't seem to have a problem. I'd also recommend some fish oil each day, again for added omega 3's which most diets (Canine and human alike!) lack. It can help with the joints too aside from all it's other health benefits.
If you're actually interested in feeding raw full time, we've got a great board on here dedicated to raw who could help you out.
Besides the health bonuses, it can also come out cheaper to feed than kibble!