Well.. the only way to actually gain PL without fighting someone would be to join a server that has PL Catchup engaged.
What this does is, every time you die, the server will give you a PL that's close to the server average. So, if everyone else is fighting, and gaining PL, then the server average will very slowly rise as well.
This really isn't worth all the trouble, though.
You can also create a server of your own, add bots, and put them on Idle so they don't fight back. Then you'd still have to battle, but you wouldn't get hurt.
You could also play CTBD mode & wish for power (each time you wish for power it's +1million pl). However you shjould go through and learn the aspects of the games combat. Take a look at the esf-world flash guide and practice against bots. Rasie the bot skill each time untill you find the bots to be a walk in the park. After that you should be ready to prety much play online at a pretty good compeditive pace.