Heya, the thing is that there are so many crypto apps that people use that would make it quite difficult for you to choose and pick but you should know which one suits your needs better
The list can be overwhelming so thus I'll provided you with an article which lists some common and some less common ones that people often use, you can read about them here: https://themoneymongers.com/best-cryptocurrency-trading-apps/

Alternatively, if you just want an app with lots of different platforms that you can then choose which one to trade on, depending on your currency bestchange may also be a start   
They have over 300 verified platforms in one place. Anyways, I hope my response together with that of others will help you choose whichever one you think is best for you!

Best of luck