Never having driven a 7.5 tonner before, I was wondering if the gearbox is more akin to that of a van, or a (Class 2) rigid?
What I mean is, do you pull away in first and drive it as you would a Transit van or car, or do you pull away in 2nd the same as other heavier trucks? 
I would say they are small trucks as opposed to large vans therefore you should find the gearbox more like a class 2. I’ve always used 2nd gear to pull away in (unless fully loaded etc. of course) and had no problems.
2nd gear start on flat, unloaded etc etc but the rest of the box is much like a van.
Of course every vehicle is different, but of those 7.5t that i’ve driven, they all lack the torque to use the box like a larger truck. The ratios also tend to be spaced further apart like a van so missing gears out doesnt work.
In my experience most 7.5tonners you drive like a van - you almost always start in the lowest gear and use all of them on the way up.
Paul
most 7.5tonners you drive like a van
Yes like a complete nutter 
Drive the truck the way that feels right.
If you’re pulling away in 2nd but having to keep the clutch balanced on the biting point for a long time to stop it stalling, then you should be pulling away in 1st. If you’re pulling away in 1st but almost immediately changing to 2nd, then you should probably pull away in 2nd.
If you’re skipping gears on the way up but having to get the revs quite high before the change to avoid the engine lugging in the new gear, then you shouldn’t be skipping gears. However, if you’re spending more time changing gear than accelerating in gear, then you should probably be skipping gears.
The gears you need will probably be different depending on how the truck is loaded (or not).
Different trucks and different gearboxes like to be driven in different ways. Learning “vehicle sympathy” (as it’s called) is part of the skill of being a driver.
I drive a DAF LF 7.5 tonner all the time at the moment. I find first is best on that. I hate it with a passion…I want a proper lorry! 