First off, congratulations on baking your first loaves. There is something fundamentally engaging and enjoyable about making your own bread. After my first loaf, there was no going back.
What you will come to discover is that while basic bread has so few ingredients required, varying each one of these ingredients, as well as the time spent preparing, rising, baking, etc all contribute to vastly different types, flavors, and purposes.
You said your bread was a bit too "crumbly." I assume that means that when you cut it or eat it, it tends to fall apart a little bit? If this is the case, I would maybe guess that you are using a little too much flour. For a normal loaf, you only want to add enough flour so that it is possible to handle the bread. The best way to do this, I have found (I dont have a machine, only hand kneeding), is to slowly add flour and mix until the mixture pulls away from the bowl and is a round clump on your mixing spoon. I then drop it onto a lightly floured work surface and begin kneeding. It should be sticky, but continue adding very small amounts of flour so you can kneed for 7-10 minutes or so without it sticking to your hands or your countertop. This should ensure that you dont add too much flour. It should be fairly light and not difficult to kneed. The "wetter" your bread, I have found, the more possibility you have to make nice, airy loaves.
Also, as you pointed out, try to add your fat (oil, butter, etc) during the mixing process and not during the kneeding. I have found that adding it during the actualy kneeding process tends to make a heavier, harder loaf.
The best advice, however, is to keep trying different variations. You will be surprised at how much difference in texture and flavor will result from small changes. I would also recommend reading some of the other threads on DC, there is a WEALTH of information you can not find in a recipe. Personal observations, discoveries, and above all, costly mistakes that people have discovered.
Good luck with your future loaves!