Like all consoles, the Gameboy Advance was designed with a traditional controller with tactile buttons in mind. Therefore, to get the best experience, we recommend using a controller. After all, the emulators here support controllers for a reason. If you're looking for a controller, check out some of the best controllers available for Android.
You can definitely get by using the on-screen controls. Many of the emulators listed above offer on-screen button customization.