Bet-sizes are most often viewed as a percentage of acct net liq, eg my acct is $100k, so I want to put 5% into a trade ($5k). Most traders/gamblers use the kelly criterion to size their bets (size increases with edge). Read books by pro blackjack players, gamblers are often more disciplined than traders when it comes to managing a bankroll.
Gambling is more left-brain/analytical; while ...Trading... can be much more ambiguous, and complicated
Really depends on what markets, how strong you feel about the direction, the strike price, your projected price for the underlying. How much risk? The options delta and time value....
Novice traders and greedy gamblers put on position sizes significantly larger than the long term successful pros would ever dream of which is why 96% wash out. My risk is approx 1% MAX of total capital per trade: so as an example I would never take a position size of more than 1 ES contract per $100k of my capital. When I hit 10-20 losers in a row it is just a draw down from which I always been able to recover from - If I sized up any larger I will be on the road to ruin.
I guess you can still limit loss on a naked put by putting a SL. If you can't (Manage your risk) then don't trade it. Simple. Only rookie expose themselves to unlimited / unbounded downside.
A stop loss isn't an ROI tool because the whole point of options is gap risk. If gap risk didn't exist there would be no need for an options market (you can synthetically create options yourself). You can use stops to mitigate gap risk. So if you say sell a naked call and in the after hours the stock gets taken out for a hundred percent premium (like LNKD) then your stop is meaningless.