First venture into graphics overclocking -- hoping for advice

I just added a Gigabyte GEFORCE GTX 950 graphics card with 2 GB of memory to my computer. Since this card came with an overclocking utility (Gigabyte OC GURU II), I feel almost obliged to make my first venture (not counting learning how to speed up or slow down mechanical household clocks as a kid) into overclocking.
So far, I've just been piddling around, making slight adjustments to the GPU and Memory clocks, but the utility will allow me to tweak core voltage, power target and fan speed as well. Baseline settings are 1203/1405MHz for CPU clock, 7000 MHz for memory clock, "auto" for fan speed, and 100% for power.
I selected the "Really Yard Work" career scenario from the Cologne-Coblentz route as a bench-marker, since it involves shunting in an enormous and densely packed yard area. The card's standard settings yielded 8-10 FPS (measured by Fraps), depending on camera and view angle. So far, by boosting just the CPU clock to +40 (1243/1445), I've managed to raise this to 12 or so (and lower it to 7, by the way). After each setting change, I've launched TS2016, checked the results, and shut down TS2016, but should I also reboot the computer before each setting change?
Any additional serious advice (other than putting in a new processor or other component for now) will be welcome.
System: Gateway IPPISB-VR motherboard, Intel Core i3 2120 processor @ 3.30GHz, 16 GB Dual-channel DDR3 @ 665MHz.
So far, I've just been piddling around, making slight adjustments to the GPU and Memory clocks, but the utility will allow me to tweak core voltage, power target and fan speed as well. Baseline settings are 1203/1405MHz for CPU clock, 7000 MHz for memory clock, "auto" for fan speed, and 100% for power.
I selected the "Really Yard Work" career scenario from the Cologne-Coblentz route as a bench-marker, since it involves shunting in an enormous and densely packed yard area. The card's standard settings yielded 8-10 FPS (measured by Fraps), depending on camera and view angle. So far, by boosting just the CPU clock to +40 (1243/1445), I've managed to raise this to 12 or so (and lower it to 7, by the way). After each setting change, I've launched TS2016, checked the results, and shut down TS2016, but should I also reboot the computer before each setting change?
Any additional serious advice (other than putting in a new processor or other component for now) will be welcome.
System: Gateway IPPISB-VR motherboard, Intel Core i3 2120 processor @ 3.30GHz, 16 GB Dual-channel DDR3 @ 665MHz.