Stock Option Strategy

(Note: I have real money experience with options going back to 2000, first covered calls in my IRA and then long calls in my cash account though no day trading experience with real money. I have the 25K to park in an account to satisfy the pattern day trader rules and another 10K to make the actual contract purchases.)

I have a job that allows me to keep an eye on the real time stock market. Starting in January I started playing with the Virtual Trading engine at OptionXpress, daytrading options on SPY. My strategy is rather modest; I buy 5-10 ITM contracts, either put or call depending on market direction, and sell when I see the trend reverse. I chose 10 contracts because I believe that with an order size that small, if I submit a sell order at the bid it should fill immediately unless the market is moving very fast allowing me to lock in a profit if the trend reverses. I open one position at a time, I never leave my desk with an open position and I am 100% cash at market close every day. I use SPY because being a basket of 500 stocks it is buffered from sudden drastic moves in price giving me time to get out of a position with minimal loss if the price goes the wrong way on me. My immediate goal is $100 after commissions per round trip, a target that requires only a $0.15 move in option price. I don’t always guess right on direction, 4 out of 5 is typical, and I am netting between $400 and $500 a day on 6-7 round trips. My $5000 initial play money stake has grown to about $15,000 since 1/19 when I started doing this seriously. I won’t get rich doing this but over the course of a year that is an extra person’s worth of income for my family. If it lets me do nothing more than pay off my house and fund future college for my 3 kids it is worth it.

Now that I have proven to myself that this seems to be a reasonable strategy I am trying to understand what I can do better and am now in the area of “I don’t know what I don’t know.” I know about Level 2 quotes but if these are something that can help me I am not clear how to use them. I know that there are all sorts of indicators that technical traders use but I don’t know if these scale down to the day trading level. I know about the existence of the Greeks, and while I understand roughly what the numbers and equations mean, I don’t know if these will help me on positions lasting 15 minutes or less.

My main interest in posting this question is to find out if there are tools I can use to help me make better choices about getting in or out of a position or tell me more about what the market is doing. This strategy seems to be working okay and if I can translate this to real money I will consider myself successful. I don’t want to be greedy but I certainly would like to know if I can do what I am already doing more effectively.

I spent time on 888options and optionetics.com but it seems much of the content out there deals with strategies like spreads, butterflies and condors, things that simply don’t apply to what I am doing. I know there are options day traders, even some specializing in SPY, who read these questions, and I’d be appreciative if I even had a list of books or even just some things to go research and learn about that you have found helpful in your experience.

Thanks for reading this far and any help y’all provide.
I definitely understand the problem with fills; in fact, I asked a question about that here the other day. I had noticed that I could put in a sell at a price like 3.10 and a minute later see a bid/ask spread of 3.15/3.20 with my sell order still open. My only thought was “What the ****?!” I was told by another answerer that in reality, on an order that small an ask below the bid would never stay open on something as liquid as SPY.
Regarding filling at the mid, on SPY I could live with this. The options on SPY move enough intraday that even if every buy order filled at the ask and and sold at the bid I’d still make money because I am looking for moves of .15 on options that can move .30 or more in a short time. I’ve gotten good enough at picking the trend direction that I will buy options that are 3 or 4 points ITM. This gets me my .15 or more move with only a small move in the price of SPY.