You can walk into the red portal or use the /rtp command to find a random location in the world to start building.
The /smp comand will bring you back to spawn.
Homes can be set via the /sethome command. Addional homes can be set using /sethome name command.
You can teleport to your home via the /home command
/back command will bring you back to the last spot you died or teleported from.
Crate Keys can be purchased upstairs in the spawn building with your Coins and Gems.
You can always use/lobby to return to the main lobby.