Android is the largest mobile operating system used worldwide and is a great choice if you want to start building smartphone applications that will be relevant in Rwanda.
First things you'll need to learn Java, so you should pursue the tutorials there and feel comfortable with the syntax of the language before diving in.
It is very difficult to build a good mobile application if you yourself don't use a smart phone. So it is recommended to get an Android handset to carry and use on a daily basis. Any of the Samsung handsets are good choices, they are well supported and some like the Galaxy Mini can be bought for about 80,000 RWFs.
Once you have those things covered, here are some resources to start:
The best way I've seen to start learning Android is to read "Learning Android", which is available in the kLab library. Note that books in the kLab are for use ONLY while in the kLab. You may be able to find a PDF available on the internet.
There is a very complete set of tutorials available on YouTube which step you through building Android applications step by step.
Lars Vogel has a series of tutorials available covering many different topics.
Help at the kLab
These mentors can help with any Android questions you have: