Completing quests will help you in your journey, and will also give you valuable rewards.
You can choose to hide any completed quest lines with the checkbox via the Hide Completed option.
Elethor has repeatable quests, which can be done on a Daily / Weekly basis. Otherwise you should follow the main quest line.
Some quests cannot be done before others, and if you have started a quest line, you can only complete them in order from top to bottom.