in my openion you should hold this btc of $100 USD and then sell it after its price up . in this way no need to any marketing risk like in trading .
This is probably the safest suggestion on how to make it increase in the amount you have without any risk involved.
That is probably the safest way but that is not the best way for growing them as the price might take a lot of time to increase so that would not increase just $100 to a larger extent as trading can, it is always better to trade that amount to make them grow gradually.
It is the safest way yes, it is plainly as holding and it is going to be better if you are going to work for your bitcoin rather than you are going to hold it and going to do nothing. And the best way to make money with that capital is to do trading for it. Because if you are not going to do something about it you are not going to earn from it.