personally I first buy healthy food that I like, it can be easy to make therefore reducing the temptation of unhealthy food as it’s the ‘easy choice’, then also reduce the amount of unhealthy food available for choice, out of sight, out of mind!
All my elders who have ever advised me on breakfast have always included the word ‘egg’ so I started there. It is also so filling and satisfying that the craving for sugar cereals lingers no more.
It was really hard. But I find that the less accessible I let those unhealthy foods, the more inclined I am to commiting to fully eating healthy ones.