This is a game of Guilds competing over territory control and resources of the Map.
Communication and cooperation with your Guild members is crucial in order to succeed. You can communicate with your Guildmates in your Guild Chat.
In the beginning, you should focus on growing a bit stronger before charging headfirst into attacking. Early on you can have Heroes performing various tasks on the Map outside of your Base and do your best to complete as many missions as possible, as they give Resources and Gems. First off, start by defeating low-level Crooks to get a good amount of loot, Fame (if a Territory Control event is live), and get a good taste of battle. Then pick a few mining nodes close to your Base and send your Army to mine them to get some more Resources.
Meanwhile, you should also consider building and upgrading your Base Buildings, which you can read more about here.
Once you've gotten your economy up and running and your Barracks are full of Units you can start thinking of expanding your territory in cooperation with your Guildmates and prepare yourselves for fighting over Outposts. Remember to scout any potential targets before committing to an attack by sending your Squad so you know what you are up against!