Breakfast is something relatively easy to prepare in Mexico.

Molletes (as someone already mentioned) are very easy. Heavy refried beans (canned is fine, or you can make and store your own - it's a staple you eat often), cheese (any kind that will melt), Mexican broth. Top with a variety of salsas.

I make Mexican omelettes all the time. If you can make an egg fried on both sides, you can do it in minutes. Fry the eggs as usual, but before you do, put a little oil in a separate pan, enough to cover the tortillas. Put the tortilla on the heat and fry it (over medium heat, just let it sizzle). About 20 seconds, then it will get as hard as a tostada. Let the excess oil drip off, then sprinkle a little salt on top.

Then put the eggs on top and put salsa on top. You can eat it with a fork, or (carefully) like a taco.

Tacos are easy to make and take about half an hour, plus oven time. Do the same as you would with Mexican fried tortillas (fry it lightly so it's still flexible, but doesn't crack), then fill it with shredded chicken (or any meat, beans, or dish you like). Then pour on a bunch of salsa (and usually some extra water mixed in, top with cheese, and put in the oven.

While you're learning, it's good to buy jarred salsa (good brands like Herdez or La Costena).

But as you learn more about Mexican cooking, you'll find handy in your kitchen onions, tomatoes and sticky fruit chutneys, garlic, beans (black and pinto) and tortillas, cilantro, oregano and parsley, cinnamon and lime, several types of Mexican cheeses, creamy fresh and sour cream, and a wide variety of peppers, especially jalape?os, ancho peppers, and Guajillo Habaneros, which offers most of the basic staples that you can use every day to make a variety of Mexican dishes. Buy different meats and mix them with other spices.