Is being asked to pay for business supplies via Bitcoin an employment scam?

This is scam. Companies do not offer jobs without qualifications. Plus asking you to pay by bitcoin is scam and can't be traced. Even bank transactions are difficult to recover.

Don't transfer anything bitcoin or bank transactions or western union. Stop all communications before you give more information.

I'm sorry to hear that someone took (or tried to take) advantage of your willingness to trust, but that's how scam artists like this work.

Your post doesn't say exactly WHAT "supplies" you were supposed to buy to do the job, but whatever they were doesn't change the fact this was simply a way to con money out of someone. And unfortunately they are successful with it often enough to make money at it, which is the worst part.

As an employer (and one who has a number of people working for me from home on a contract basis) I would NEVER, EVER ask them to pay money for whatever's required to perform their job duties.

That being said, I do require them to have specific things, such as a telephone, a computer, and so on, but those are not things they buy from me.

Until more conventional methods become mainstream for cryptocurrency transactions so that there can be some kind of "safety net" against fraud to some extent or another (although nothing comes to mind right now and probably never will, as far as I can think of), they will remain the "go-to" method for most scams to utilize. You can track transactions, but you can't know WHO is on the other end, and what would stop them from setting up accounts just long enough to pull off a scam like this for a little while, cashing out, and moving on to start all over again?

Again, I'm very sorry you had to deal with this, especially in light of your desire to work and develop the experience necessary to obtain employment with larger, more established companies. I hope it works out for you!