The other day Amazon had a keyboard on their free app of the day I believe called thumb keyboard 4. It's like 2.50 normally, but if you are looking for a good alternative to the default this is really nice. I put it on my phone too.
There is a default mode similar to the standard one, the thumb layout which splits it in half with numbers in the middle. Super easy to type on. And there's a 3/4 size off set one hand layout where you can hold it with your left hand and peck away with the right which is also quite easy.