Okay, here's a tip. You can't modify a xml file and expect the changes to take effect during a game. The xml files are ONLY read at the start of a new game when the world is created.
For example. You want to change the starting gold that each fraction starts with.
1. Go to your Startdock Games\Elemental\data\English directory
2. Find the file ElementalDefs.xml
3. COPY this file to your user directory (on my Win7 system this would be: Documents\My Games\Elemental\Items
4. I renamed the file (but you don't have to) to ElementalDefsNew.xml
5. Open the file in Notebook and change 100 to 300 in the line that looks like:
<PlayerStartingMoney>100.0</PlayerStartingMoney>
6. Save the file.
7. Start a NEW game. When you do, any changes you have made to that ElementalDefsNew.xml file will be read into the game.