Companions are a great resource. They can provide buffs, healing, stat boosts, and more. To make the most of your companion, you need to do some research and ask questions to other experienced players to find what the best fit is for your character. Companion selection varies by your role. There are a LOT of companions out there to choose from! As you start out, I recommend using the best companions you come across and leveling them up as you go along.