When starting there's quite a few ways to begin, I'll list the primary few below!
You can begin by exploring spawn, just wandering around and meeting the community! You never know, someone may even be nice enough to gift you something - though that doesn't mean demand items!
To choose this just run the command /warp spawn, this can be done whenever from wherever!
You will have to move to Option Two after this, this is just a fun way to meet players!
Don't take from any shulkers/chests at spawn and please don't mine any unclaimed blocks. Either may result in a ban, especially stealing.
2. You can begin the standard way, punching down some trees and getting setup!
To do this first run the command /rtp - this will take you to a random location in the wilderness where you can begin to make a home. Run the command /sethome name (replace name with whatever you wish to name that home). This will enable you to run the command /home name to get back to that area!
Move to the guide on resource worlds for information on mining/resource gathering!