if you want to invest in bitcoin, don't look at the value just invest, don't be fooled by the market swigs, there are only two things to do with bitcoin now that is buying and holding
keep buying no matter what the price it, and hold the rest, if you want to make more bitcoin from the one that you are hold, invest them in some other things like altcoin that have a great potential or mining
actually i never bought a single bitcoin, i like to generate them via mining, it's more anonymous for me, and more profitable, even if it's slower
In my own opinion, i agree that you should not be fooled by market swings. Because in bitcoin it is decentralized which means it doesn't have a fixed price. It always swings up and down. The best time for me to invest is when I think (based on the chart of the price) it is low price for me. Because when the price of bitcoin goes up that's the time to sell it. But i also recommend you to invest in mining.