What do people do post-PPL?
GPS...
The less flippant answer: For anything more than 100nm-ish, I plan the flight in Skydemon and print off the PLOG. Have skydemon up on the ipad, and programme the route into the onboard GPS. Then at each turning point, sanity check the GPS (map to ground); Twist, Turn, Time, Talk; noting the ATA and setting the stopwatch to monitor the next leg.
I still fly the calculated heading (using the GPS to correct), and could trivially drop back in the case of GPS failure/jamming (as briefly happened to me the other day just west of CPT). The onboard GPS gives me very accurate and reliable tracking, and skydemon on the ipad gives me airspace avoidance.
(Although the gauges in the aircraft are really not that accurate, so that fuel planning has to be taken with a pinch of salt, and a huge reserve in any case.)
Install some kind of fuel totaliser... I'm having an EDM put in next week - up until now I've operated on at least 1.5 hours reserves, with a 10% fudge factor (the TB10 fuel gauges are completely non-linear). The added benefit is that accurate leaning should now be possible, hopefully saving a few percent.