Hi Vasilis! Thanks for playing the game and taking the time to understand it. Sorry about the confusion, we realized after getting player feedback that the game is not beginner friendly, and we're working on the game now to improve in that area.
The combat has a rock-paper-scissors type of mechanic where the 3 elements are strong/weak against each other. If the player matches the elements properly they can do massive damage and take very little damage. Sadly the difficulty curve on that game wasn't adjusted properly so its really tough for new players to do well. We will fix this problem after the jam for sure.
You get the crystals (called gemstones in the game) from other civilizations. We treated this like a "money" value so you go to planets with civilizations and then either trade with them, subjugate them, or destroy them in combat to get their gemstones. Mining and hunting have a chance of giving gemstones as well but only if you perform really well (research makes this a bit easier). We will do our best to explain all of this in-game in a natural and intuitive way!
As for the other builds, yes we will provide downloads for all major platforms after the jam. Right now we are focusing on fixing all the bugs and improving the new player experience. Thanks a lot for your feedback and compliments, it means a lot to us! :)