Buying power: cash in account vs margin trading

I'm relatively new to options. I have been doing well so far with vertical puts and I like the defined risk. however I recently ran out of margin. I have more funds to add to my account. However, I don't want to have a pile of cash just sitting doing nothing. If I add in $1000 cash (easy number to work with for this example) into my account, that would give me another $1000 of buying power to do without using margin. However, if I invested it in SPY or VOO so it would work for me, would I only have $300 in additional margin/buying power due to the margin requirement %? What is the smarter play? Apolgies if this is a stupid question.