So give me one good reason why I'd want to buy Bitcoin?
Basically there is a good chance that if you buy Bitcoin these days, you'll be able to sell in a couple of years at 2x - 5x price. Which is not bad for a speculative investment.
If you have the appetite to speculate or if you are a tech dreamer, there are plenty of reasons to buy.
The main players I see out there now are Blockchain.info and Coinbase.com
Of course there are dozens of other players, but it looks mighty like those two are the top players in the Bitcoin field. I know I'll be corrected on this, but that's what it looks like to me.
There are many big players in the Bitcoin world. It's a huge lot of money to work with and there's still a lot of room for much more big players.
I'm not sure of the reasons behind putting together a website offering (basically free) services - mostly chain explorer and wallet - and an exchange (which by chance also offers wallet).
There are a lot of wallet providers, some even offering debit cards (Visa/Mastercard compatible), there are a lot of exchanges, but also a lot of other businesses in this world. Today's news is that even PayPal tries to get a slice of this pie (and all major financiar services will do the same, sooner or later).
The Other Player that seems to be gaining ever more traction is the Ethereum parties. The ethereum-wallet people, and so on.
You have to read more. I am not certain that Ethereum is a safer investment. I see it even more volatile/speculative than Bitcoin.
You were asking about mining. 2 weeks ago everybody would have told you to buy many GPUs and mine ETH. Yesterday and today its price dropped a lot. So it's not a safe bet anymore.
But that doesn't mean you cannot mine something. But this is the problem: you have to find that something. You need patience, since you may earn pennies every day, you even have to check if you don't pay more for electricity than your earnings. But the good news is that there are plenty of altcoins that can still be mined with GPU, which is a smaller investment than a Bitcoin miner and you can resell to gamers too.
However, this needs reading, calculating, and reading more.
If you already have a very good GPU (or you know what you want to buy), go to the support threads for various GPU mining software for that kind of GPU. People in there could help you from setup to where to check what's better to mine.