Best degree to become an investment Banker
To put it simply, an investment banker is someone who advises companies on fundraising activities or mergers and acquisitions. An investment bank is a broker that facilitates these transactions and connects people with capital (investors) with people seeking capital (companies). These transactions for fundraising can come in the form of equity transactions (IPOs, rights offerings, block trades) or debt transactions (investment grade, high yield, convertible debt, loan syndication). Other advisory activities can include restructuring, delistings, acquisitions etc.
Entry level investment bankers come from a variety of backgrounds, from English and Physics majors to Economics and Finance. The type of degree is not typically as important as the pedigree of the school you went to. It's a sad reality but top bulge bracket banks typically only do on-campus recruiting at the top schools, and having a stellar GPA and internship experience from a top university is your best shot of getting in. It doesn't matter if you majored in something completely irrelevant as long as you are able to demonstrate keen thinking and relevant experience.
That said, it is not impossible to get in from a non-target school but you have to work harder. You have to be willing to network and put in the hours to build your network within the industry. I have written multiple other answers to how to get in if you're not the "typical" candidate on paper so you can refer to those.
Finally, as for CFA certification, it is really unnecessary for getting into banking. CFAs are generally necessary or preferable for equity research type of positions but for investment banking it really wouldn't make a dent. I would personally recommend spending that time elsewhere, like networking with the right people and learn the technicals of financial modeling to ace any interviews.
Someone from journalism major can definitely have a chance of getting into an investment banking career. I would supplement it with the right type of experience that is relevant and network your ass off to maximize your chances of an interview. Then it's all up to you to impress the judges and earn your spot.