Hello, I don't think you need to 'pump' real money into SL to have fun with it (except you really, and I mean REALLY care about how you looks, like me:P) there are TONS of free stuff in SL, free clothes, skins, hairs, etc.. And a lot of things to do!
And getting lindens in SL is fairly easy if you know how (though it's much more convenient to just buy them, of course) just today, I earned 1000+ L$ by giving out free share-able stuff to people, because some people are kind enough to pay for them! ^^