The Google Slides, Docs, and Sheets templates available in the web version of those tools is now available to you in the Android and iOS versions of Slides, Docs, and Sheets. Tap the red “+” button to create a new Slideshow, Document, or Sheet and you’ll be presented with the option to create from a template or create from scratch.
As someone who gets frustrated by manipulating spreadsheets, I find the Sheets templates to be particularly useful. The Docs and Slides templates are also helpful when I need inspiration for layouts and color schemes. One of the Slides templates that I frequently use is the student certificate template.