I know nothing of graphic design.
I’ve started developing for Android, and I want my interface to be beautiful, and for that I know it needs to be designed by hand, but I also know that means knowing how to do design work.
Is Illustrator the right program to start learning? Is that used for this? To my surprise I actually didn’t see any information on the subject after some googling. Everything you look up about “interface design for Android” tells you how to arrange buttons and menus and things like that, but not literally how to make the visual elements.
Illustrator IMO is a top choice for graphic design because is great for making vector art that is scalable, and it actually contains lots of features that will allow you to achieve a 3D/artistic look with gradient mesh, blending, and various filters. It gives you a crisp clean edge to your work, which is important for UI elements like icons and buttons, especially when you need to scale everything into exact pixel sizes across multiple devices with varied screen resolutions. Another great feature is “artboards” which allows you to have multiple designs in the same file, but export them conveniently into separate PNG or PDF pages without slicing.
I think your search results are returning UI/UX design tips for mobile app development. UI/UX is a very different field than graphic design (with some overlaps). You will need to search more specifically for the effects you are trying to achieve in the visual elements (i.e. grunge look, retro embossed font, gradient, fabric look, etc.).