One of the biggest fallacies is the relationship between implied and statistical volatility. If you trade with the idea that if implied is over stat and you sell the options because of that and vice versa buy options when the implied is less than the stat, you will have a financial lesson that will be devastating. Not saying this is the case 100% of the time, but implied leads stat about 90% of the time. Example, say the stat volatility on XYZ is 45 and the implied volatility is 55. Well, these options are overpriced right? Wrong! The implied is telling you that the marketplace believes that the stat volatility is actually going to increase that is why everyone is buying paper. Now say that stat volatility is 55 on XYZ and the implied volatility is 45, well options are too cheap right? Wrong! Paper is getting sold and they are selling it because they believe that the stock is going to settle down and not move as much. Do not trade options by comparing the stat volatility to the implied volatility except to buy the options when they are over their stat and sell them when they are under their stat.
As far as being short gamma, there are many ways to earn the premium on options without trying to steal the theta. Why not sell the vega? You will profit from eroding premiums without exposing yourself to a stock halt pre-open that could put you out of business. Best thing is long gamma because those gaps can make your entire year, and when a stock breaks out and runs, you can have a money printing machine on your hands. And if you’re still not happy, add a ratio spread on Friday to hold over the weekend on your front month premium. Then take it off on Monday. At least you reduce your gamma exposure 4 out of 5 days a week and can collect the weekend premium. Most floor guys if they want to earn the theta will put on back spreads. This way, they can capture that front month premium around the strike and if the market takes off or the stock gaps, their position will become a long gamma position and they won't get hurt. So they essentially are short gamma short premium around the ATM strike and if the stock runs or gaps, the position becomes a long gamma long premium position. This is how guys avoid blowing up on the floor. This stuff is absolutely critical to understanding options. There really is not much room for error.