The Best rescource for any question in D3 is
https://maxroll.gg/category/guides
https://maxroll.gg/resources/season-start-1-70-leveling-guide
you find tips and guides for every topic aspect and build in the game.
The leveling guide will help you even, if you already are lvl 70. Also if you start a new char you are able to give him basement via adventure mode and then switch to campaign for an easier start.
Everything you got in season will switch to non-season, when season ends. So for a beginner it is even more useful, to start with season (and get a full set via Haedrig’s Gift wich brings you up to torment 6-10 very quickliy … but do the full season journey to learn all functions of the game and earn up to 5 stash tabs permanent.
Ask in the chat that you want to join a beginner friendly clan. That will help you much (even if you mostly want to play solo).