There are several points to consider:
There are far more PhDs who want to be professors than actual open positions, so most people won't make it. Just take it as a fact of life, and don't be frustrated when being rejected somwhere. It also means that there is no universal career guideline that is guaranteed to work.
While a PhD is a compulsory badge for you, earning another PhD in most cases won't add add much to your CV, so if you have enough flexibility in choosing a research topic in your current program, stick to it.
During your PhD studies do you best to build up your own research profile. Find a problem you like, achieve progress, publish in the best journal/conference that is ready to accept your work.
It is almost equally important to build up your network. When you have a chance to meet colleagues from your domain, do it, and keep connections. If you can collaborate with someone outside your university, take this chance.
People will judge your CV on the basis of its objective merits (whether your research results are good enough according to some reasonable criteria) and your "fitness" for the particular institution/group. Thus I don't think you should focus or general presumptions that there are higher chances to be hired in a field A rather than field B: it all depends on your personal achievements and your target institution profile.
Personal connections do matter, employing someone you know is a safer bet, of course. In general, be ready to more across countries, and accept postdoc positions — no matter how you look at them, it's better to be a postdoc than to have no job or go to industry (if you wish to stay in academia).
As you spend more time inside this system (as a PhD student / paper writer / conference attendee), you'll gain more understanding of your personal goals, I believe. It's quite natural that your current picture of the future is vague, but it will clear up as you go.