I'm also always happy to help interpret data. I've spent a fair amount of time analyzing AIM and MoTec data. I've also attended numerous classes on both and have read a majority of the top data analytic books. I love data.
That being said, looking over lap times with GPS is good, especially if your learning a track and figuring out the driving line and/or braking zones. To improve the chassis, engine, suspension and brake performance, you'll need a lot more sensors. Steering position, front & brake pressure, throttle angle (typically via CAN to the engine ECU), clutch position (option), temps and pressure sensors on the engine (oil temp, oil pressure, fuel pressure, fuel temp (optional), water temp and trans temp. For the suspension; shock pots or load cells, ride height and/or aero effectiveness sensors.
For the brakes; tire temp & pressure, brake rotor or caliper temp sensors
I could go on and on but you'd be really surprised what the data can tell you. I provided a few examples on the build thread for my yellow car (on the old ITRCA site) of how the data was showing me the performance of my engine oil, the effectiveness of my oil pan & baffling on counter clock wise tracks, the performance of my brake fluid and the impact it has on the front & rear bias, undetectable wheel lockups and overly aggressive turn-in and the impact it had on the suspension effectiveness in the exit. I got all that data from one track day (two sessions) and about an hour or two of analyzing the data at home. Here's a few screen shots as an example:
Effectiveness of engine oil grade & brake fluid performance as the operating temperatures change
Undetectable loss of traction under deceleration
Performance impact of late braking... leaving too much on the table
For what it's worth, I currently own the following systems and/or actively use them:
Hondata S300 - installed on the yellow race car & one of my daily drivers
MoTeC M4 Pro (advanced telemetry) - was installed on the drag car
MoTeC M800 (w/ advanced telemetry) - currently installed on the drag car
MBE 941/970 (w/ advanced telemetry) - currently installed on the ELR/Foss-Tech race car
STACK STACK STACK 8100AR (display & advanced telemetry) - currently installed on the ELR/Foss-Tech race car
Autosport Labs Podium Connect - (remote live stream of telemetry) - currently installed on the ELR/Foss-Tech race car
AiM Solo DL (w/ECU connection via RS2232 & datahub w/wideband sensor) - I use it on various cars for quick telemetry
AiM MXL2 (w/advanced harness expansions) - currently installed on the yellow race car
AiM Evo5 (w/ advanced harness expansions) - installing on the ELR/Foss-Tech race car
AiM GS Dash (display for the Evo 5) - installing on the ELR/Foss-Tech race car
AiM Smartycam HD 2.1 - used on various race cars
AiM Smartycam GP HD 2.1 - used on various race cars
And pretty much every type of expansion, sensor, etc... that you can connect to these systems.
I'm by far not an expert or someone that uses these systems for a living, but I've done my homework and have a decent understanding.