It depends if you want to BUY the option or SELL the option.
As far as I know, you only need the cash necessary to buy the option. In the US, the exchange that handles most silver futures/options liquidity is the CME. An option is thus a right to buy/sell a futures contract. One futures contract represents 5000 Troy ounces and its price is quoted in cents. Let's say that Silver right now is quoted at 17. One futures contract then represent 17 * 5000 /100 USD = 850 USD.
Trading is a process and business less dependant on the amount of trading but more dependant on the handling and knowledge of trader,. This will result and will prove practically if one person trade without knowledge with big amount and one start with normal mount with knowledge so these will give two different answers which are very clear. You have to accentuate on your knowledge and decisions, more than that of the quantity of coins.
You have nice point here we need something everlasting for trading which is only our knowledge and our skills, if today you buy thousands of coins but you have no such information that when to buy so green market buying and red trading can give you lose, so if you will have to good information about market selling and buying then investing only 50$ can earn good amount of profit for you, so you will just have to hold and enhance your knowledge when to buy, you can invest any of amount but always try to increase your knowledge and your skills at first priority.