So I bought premium today..

I don't really know what to do..
Like I've bought Shuttles but not much I can do now..

What world are you on?

Little Upsilon

Set your Game Level requirements to Peaceful, and try to get it up to at least 6-7. That'll require building an enterprise up to a couple hundred corps, but it'll get you several hundred GC. Also, fight occasional C3 wars to get your war level up as well, which is worth lots more GC, and in the process of doing this you'll probably get some monthly rewards too. This will give you the resources to expand your empire well. After that, it really depends what your goals are.

Search the beginner forum for "Aries" and you will find several guides there. They should help you accumulate assets that you can gain by being premium, especially the game level guide and "Path of a Warrior". Don't forget that if you find no other use for coins, they are worth $180+ Billion each by using them to purchase electric power on direct trade.

If you finish "Path of a Warrior", message Candinnalm on LU, if you wish, and you can join my federation. From there, I can help you grow further in the game.