Exocraft.io is an interesting multiplayer space strategy IO game freely available online for desktop users. You have a mission to build and develop ships in order to create a mining fleet for collecting resources from different planets.
The energetic gems are, of course, of the highest value, and your power will grow while gathering them. Also, you will receive points for this task. There are some obstacles included with the intention to prevent you from doing this. For example, the most valuable gems are protected by guards, and you are unable to collect them from start.
So you have to gather available ones at first and raise your power that way. Later, you can attack those with a higher value when you upgrade and develop your ships. The game producers provide an excellent manual, and you should read it before starting. You will find out all the necessary details there.