Gain More Experience
To have your troopers gain more experience after each battle, go to 
the "stta\units" directory and open the st_db_attr file in notepad. 
Go to line 26. It should start out as: 

261 0 0 15 0 0 1... 

Change this line to 

261 0 0 200 0 0 1... 

You can try other values besides 200 to tweak the experience growth of your
troopers. 

Extra Equipment
Just go to your Starship Trooper directory and then the mission directory.
Go to each mission dir and look for interface.txt files, open the file,
change the different values in equipment from 3 to 12 or 18. 
*Note: make sure once you change the value in one file, the rest of the 
files must be changed as well, if not the next game cannot be played. 

Increase Storage Depot Ammo
Open the st_db_attr file in notepad and you will see on line 29, 6 positions
back, there is 10000. Add another zero to that figure.