DOBing is a great way to get your teeth into in-play trading (horses), not a market for everyone but if you are intrigued by in-running trading (not match betting) then DOB is a good way to start.
As with every trade and every match bet, you need discipline and the ability to accept a loss or the reality of in-running trading will bite you very hard. If you have trading software you can set your exit points, I advise you to absolutely do this and remove the emotion. There is some great information out there on DOB’ing, as always be diligent with the paid for services. I use http://patternform.co.uk and https://www.timeform.com/ both are free for what you need.
I also subscribe to the fantastic horse racebase which is expensive and really for experienced punters and horse racing geeks.
DOB’ing if you follow the rules and do the research will generate a very nice income over the long term. Stay disciplined and stick to your rule and it’s a great way of adding to match betting income.