I would suggest that the best training you can acquire will be that which enhances any skills you already have, or teaches you a new skill. If you're asking about VA-specific training or certs my own personal opinion is that there isn't a single one your clients and potential clients will 'care' about or even be aware of. Anyone who tells you otherwise likely just wants to sell you something
I've been in business four years and have never had a client or PC ask about either. What they want to know is what I'm capable of - and usually that's going to be communicated to them through referrals, testimonials, and a portfolio.
With that said, I have not participated in but have heard great things about VA Classroom for social media and internet marketing, so if that's a service you're offering it might be a useful course to take - but not necessarily for the 'badge' but for the literal information it will teach you.