You should just not do it because its something that is against the rules and I think if you are doing this its very wrong and you should be punished on some way.
It cannot be illegal at this time because its not an official currency..

Well that is the reality about investing with trading the lower capital you are going to invest then the possible returns are going to be exact amount to your investment. But if you just want to try if you are going to become successful with your first try with that $100 capital then that is going to be fine as a start for your trading career.

I do not make use of Bitcoin in that way because I use it as an investment so that I can make money with them in the future.
Spending them is not a option for me because I will end up with nothing if I do that.