I want to create a space grand strategy game, similar to Neptunes Pride. I wrote basic engine for this game in python to get knack of writing a game, but now I want to start it over.

I am just a guy programming as a hobby in my spare time, so I do not want to commit any money onto this project.

So, I am looking for a starting point.

Some description about the concept of the game.

The game is essentially a sandbox strategy game. Player controls his empire and does whatever of the 4X he wants. There are enemy empires. Enemy empires are controlled by Utility-AI(each empire has different traits and responds to stuff according to these traits). For example Agressive empire would respond to events with military actions more frquently than a passive empire.

I don't belive that visual side is going to tax computer in any way. But it seems that in later part of the games development AI might take most of the processing power. So, again what should be my first starting point in making that game?

Should I learn Java and search for some library that can blit sprites and can draw lines and circles on screen? Or should I use GameMaker and somehow make some kind of AI module to it in python? Or should I learn C++ and find some open-source engine that has basic graphical features present?

The question of which language you should learn is obsolete, because with all languages you named it is possible to achieve what you want. Each language has their pro and contra to choose them. So in first you should ask with which of them you already familiar or you like most. That would be the right choice for you.

The graphical stuff you can choose a framework which do the work for you for example ogre, angle, .... etc but the logic of your game which components interact with each other or not is still up to you in all languages or gamemaker software. Plus the ai of course.

In my opinion you should start to create all visual things. The reason for this opinion is simple: you see results/progress! After you done that stuff you can still add an ai.

To expand off of what exOfde has mentioned, putting language and environment aside, I would take your loose requirements and try to turn it into a real requirements document. It doesn't have to be more than a page, but it pretty much outlines for you what need to do to go from "nothing" to prototype. Your starting point depends on where you want to start,, obviously the real starting point is pressing the power button on your PC. But jokes aside, write your requirements document and consider it your mini-bible; ideas will flow when you are writing it. Once done, pick any environment that can meet those requirements; if you want to make a prototype of the game, you dont want to have to program the engine, your goal is to show something in the end and then iterate off it.

I am not familiar with the term "requirements document". Do you mean design document?

Okay, thank you!