Feedback Tips (Stellaris: Galaxy Command)

Hello everyone! I try to delve into the game, but often there is no one to consult with:
- on the EC went into minus by Lv 7. How to fix the situation?
- according to the guide for beginners, killed 2 of 3 pirates, joined the Alliance and now I can’t attack, says you cannot move (declare war or peace ... Something like that)
- and the question about the future: is it realistic to play with a minimum investment?