Bitcoin is not a bad idea, it just happens to not be very well thought out. The same way thieves who brag about their ill-gotten swag on facebook don't think things through.
There's a limit to how many Bitcoins there can possibly be, and the closer the number of bitcoins gets to the limit, the harder it is "Mine" more of them. Mining, by the way, is how you get more Bitcoins, and it involves solving a computationally difficult mathematical problem. Each Bitcoin is a unique solution to the problem, and there is a finite amount of them, which is where the limit on Bitcoins comes from. The more Bitcoins out there, the lower the chance of finding a unique solution, and hence, you require more power to find Bitcoins.
So, because there can only be so many Bitcoins in the market, it's value goes up over time, which encourages hoarding over spending them. Its not regulated by any government, so it's value can jump and down wildly, resting on the whims of international governments, ironically enough. I wouldn't recommend investing in it.
Which brings us to dogecoin. dogecoin is basically the same thing as Bitcoin, except it's newer, so buying into it doesn't seem like such a bad idea. However, the fact that it's the 6th most valuable cryptocurrency out there should give you an idea as to just how awful cryptocurrencies are.