There are countless number of websites where you can earn using your android smartphone, as long it has all the features that would enable it to access the site without glitches, you are good to go. But first of, you need to acquire the skill sets that'll qualify you to work on these sites, because you wouldn't want a situation whereby your smartphone is ready, but you can't cease the opportunity to deliver on a given task due to lack of the requisite expertise needed to get it done.
As for the phone, you need a smartphone with good RAM of about 2GB and above, and of large internal storage space. Efficient processor of the phone is also highly needed, if possible it should have an android version of not less than 7.0.
Some of the sites you can use your smartphone to work on are answeree, because as I am answering this question, I am using an android smartphone in doing this, which I guess so many other members are doing same everyday. Other sites you can check out are: freelancing sites, survey sites, forum like zwerl, swagbuck etc.