What is a safe percentage to invest into Bitcoin? How much of your net worth is currently in Bitcoin?
We can't give you such suggestion here because we don't know your personal situation, your income, investment experience, how much you are willing to risk etc.
We can only share our own experiences and nothing else.
I personally prefer to invest here only money earned from other online business opportunities and keep this funds in online wallets.
Right now, I investing about 30 % of funds I earned on Internet here and rest of funds I investing in other places.