Well, if you're still fighting level one monsters, you don't need to be worrying about building bases yet (not that you would have enough crystals anyway).
Eventually, I think i's good to have at least one base per level (two, if you've got the money to blow). But as of right now, you should be more focused on gathering human skulls, weapons, and armor from the creatures you kill and selling them in the HQ for extra crystals.
Really the best way to learn this game is to play on a team with somebody experienced. I suggest going to Tarix's telnet site (tarix.overkill.net) and joining my team in the Novice game there. From there I can give you hints and access to my bases and better weapons.
I'll go ahead and email you the team passcode in the game...
![Cheesy](http://www.operationoverkill.com/forum/Smileys/default/cheesy.gif)