How do you get bc free on roblox

There is NO possible way to get BC without buying it. Nine times out of ten people/websites saying they give you BC/TBC/OBC are trying to scam you and steal your password.
The best deal if you want BC is to get normal BC because (if my calculations are correct) you keep normal BC longer, so you get quite the bit more robux. I do recommend monthly it is the cheapest of all and robux is consistent.