I am so in love with muesli right now! It's about the easiest breakfast to make, it fills me up, and it can be customized any way you like!
All you need is:
1/2 cup old fashioned rolled oats
It's very important to combine the oats and milk first so the oats have a chance to soften. I find that by the time I've decided on add-ins and added them in, the oats have had the perfect amount of softening time. About 5 minutes or so (if you really need a time limit).
I don't have an amount of milk for you because I've never measured it. Just pour a little in until the oats are covered. Remember that the oats are going to soak up some of the liquid so if you want your cereal more liquidy, like typical breakfast cereal, you should add more milk. I prefer it if the oats soak up almost all of the milk so I err on the lighter side. It would probably take you a couple breakfasts to figure out what you like best. You can also use any type of milk you want. I've used unsweetened soy milk and plain almond milk.
Once you've started your oats softening, you can go ahead and add whatever the heck you want! Regardless of what I'm adding, I always start with a teaspoon of vanilla. It really adds a nice flavour. And while I've tried other extracts, vanilla is the only one that doesn't taste out of place (or strange and alcoholic).
I also prefer to sweeten it with sweetened shredded coconut. It's weird, I know. But it adds a nice flavour (cuz I love coconut) and I've found that it's easier to measure out and combine with the whole mixture than honey. (Although honey is very good when I've used it.) Of course, you can sweeten your muesli with regular sugar, brown sugar, Splenda, or nothing. And if you're adding really sweet fruit like bananas or raisins, you might not even want to bother. Again, this is really a breakfast option that's customized for you. You make it the way you like it!
My favourite bowl is cinnamon raisin (with almonds and coconut, obviously) and it's kind of my default bowl if I've run out of fresh fruit. But that's cool with me cuz raisins are like candy!