As far as investing... That is tricky. "Investing" in BTC is extremely risky and you should be prepared to loose everything. Bitcoin is not designed as an investment, it is a payment system and I would recommend thinking of it that way. But if you want to do it anyway for fun or whatever. Then start with 1 bitcoin and try selling it high, then buying it back low. Make a game of it!
Not to pick a fight with RodeoX, but I would completely disagree with that assertion. Yes bitcoin is used as a payment system, but like all currencies, whether fiat or virtual, they have some nominal value beyond their use as a form of payment, which fluctuates over time in relation to the other currencies. If you can trade currencies, and exploit fluctuations to your advantage, then it is a perfectly reasonable investment vehicle, just as if you were trading USD-GBP, EUR-JPY, or leathermugs-tin hats. Yes it has risks, as all investments do, and you certainly don't want to over-extend yourself or lose more than you can deal with. But you can always manage risk as well, for instance when trading you can put in a stop-loss order, so that you only risk X percent. I think that bitcoin today is on par with some of the riskier fiat currencies, so I say educate yourself, then go for it.
I will stick to my assertion based on the word "designed", but I think you are right about investments. A cool thing about btc is that it can do anything money can do and more. Using it as an investment vehicle is perfectly reasonable. Just be careful. Bitcoin is a hyper liquid experimental market that swings wildly. And unlike a big bank, if you loose your money the government won't come in and reward you with my tax dollars. hehe