You probably could figure out what specifically you yourself would enjoy using and which you can't find on the market.
At the technical side, Google provides pretty good resources to begin with. Google for "Android Building Your First App" and follow the first link from the search results. There will be a pretty comprehensive tutorial there.
First thing you want to do is make sure you get Android Studio as your IDE. Amazing tools that basically write the code for you. Make sure you follow the latest trends in the design guidelines, which is currently Material Design. Something else to know: Stack Overflow is your friend
- If you have some money to spare, you can subscribe to Lynda.com, their courses are great.
- As said above, Use Android Studio as you IDE.
- Read and follow Google's design guidelines.
- You can start learning the basic on the Android Developer - Getting started guide and go from there.
Try an ebook, you can get some good ones from apress. There are plenty for beginners, and they are easy to follow.
Use this in conjunction with the android developers section and you should be fine.
For games I would recommend Construct 2.
My game made in Construct 2, exported for Android in Intel XDK and fused with FGL enhance for ad, Shadow of Orkdoor.
You can play on Google Play.
There is also trailer on youtube.
I would post links, but I am still fresh here so forum would not allow me, so you will have to google it
First, you have to code little apps and try to improve your programming skills. Like other posts said, you have to read a lot of tutorial on the net. The android.com website is good start for beginners. I will recommand you a good blog I used to develop : androidhive ! Very good !
If you want developing games (2D or 3D), I would use Unity3d. Maybe quite difficult to learn at beginning but if you read a lot of tutorial or watch a lot of videos, you would learn quickly as I do. You have to code in C# (near to Java coding style).
+1 for Lynda. The provide university quality tutorials for almost everything.
If you're not that experienced and you just want to make simple apps then you might want to consider MIT App Inventor. Just Google for that and work through the tutorials. It's a very visual platform, though it has its limitations.