Make sure you are healthy, that's the key word.
I have a friend that like to eat junk food after giving birth and cause the children to get sick often even breast feeding.
Breast feeding are the best food for new born baby(up to 2 years) especially the first 6 months.
Eat more sea water fish(once a while salmon is better as high on natural DHA, not chemical added DHA), reduce red meat like mutton, beef, pork and chicken.

Breast milk contain nutrients, where you get the nutrients? It needs to be replenished.

Sadly, I only can envy to mothers that able to breast feed their babies while my wife can't due to her stupid mother that knows nothing

But my wife don't want to listen to me, so just let it be. I've give up on advising her on this.
Eating eggs are not that good, especially got wound, should avoid eggs for 100 days.
Taking fish are good, again not on the first 2 weeks after give birth.
Fish are good to prevent depression and good DHA supplement.
I just bought a new formula milk that contains no DHA(Morinaga), way cheaper than Snow.
Still, it is chimical milk, won't be good for babies as it does not contain antibody.