Forst of all you need to decide whether you are investing for long tern or short term. Price of BTC is constantly going downwards since January 2018 I think if you are planning to invest in BTC for short term, probably you will not get desired returns. BTC is most leading coin. Invest in BTC hold your investment for months or years only then BTC will give you desired ROI in return.
Ofcourse bro!! Buying bitcoin today is still worth it, all you need to have is patience and braveness, if you have that promise it wi be worth it. But i think ethereum is great to buy today because fast recovery