It’s pretty darn difficult to eat healthy. It really doesn't help that a burger can cost just a few dollars, while salads cost upwards of ten dollars. Preparing healthy food is time consuming, and a common perception is that dietary plans or sticking to a certain type of food is the way to go. Many people think becoming vegetarian/vegan, or only eating organic foods will help in their search for healthy eating nirvana. In reality, making just a few small shifts still make a difference.
Of course, everyone is different and your dietary needs vary. But there is one simple rule to keep in mind: reduce the amount of processed foods. This ranges from sausages, hamburgers from fast food chains (who knows what goes into that patty) to avoiding refined sugars. Sugars can be substituted with raw honey.
Avocado may not work instead of mayo every time, but cauliflower mash can actually be a very close substitute for mashed potatoes. There's of course personal preference at play here.
Fats and carbs usually get the worse rap, so you may want to check this infographic to see whether that's justified. And remember, sometimes baby steps are the key to getting started.