Sorry to be that guy but “radicals” specifically refers to one of many systems for categorizing character components for the purpose of dictionary indexing. A better more generic term is “component”, since components can serve many purposes, usually meaning or sound, but sometimes also iconic or other.
A radical is often a component, but not always, and a character with multiple components can still only have one radical, and radicals usually hint at the meaning, but not always. They’re made up by some guy in history who didn’t have access to good science on character origins.
TL;DR: components can have many functions and radicals are insufficient for learning purposes.
The only thing that is completely non-negotiable is the Pleco dictionary app. There’s no real competition. The basic functionality is free, but it also has a bunch of single purchase add-ons that I think are worth it if you’re ~~psychotic like me~~ serious about learning the language.
/r/ChineseLanguage has a bunch of resources in their wiki. I haven’t checked it all out but a lot of it is good. The sub is pretty active as well, and surprisingly free from sinophobia (although there is of course some).