Be logical. People will do things in a slightly different order to each other but there's things that should be done first. For example, it's easier if you sort the pedal box before fitting the side and transmission panels.
If it was me, this how I would look to tackle it. I think your first step is to make sure you know exactly what you have and whether you want/need to do any refurbishment/repairs to these parts. Then see what major components are missing if any and you can start looking for those.
If there any homemade parts, I would double check that they will be suitable for the intended purpose and sort them out if needed.
I would build a rolling chassis that steers and brakes as it should first before worrying about the engine/gearbox/panels etc.
One tip that I've picked up - if you can, keep a small float of project money. A common reason for projects stopping and starting is lack of funds. It might be hard to keep the enthusiasm going if you have no money to put towards the build for a month or two. Plus, if a bargain crops up, you're in a position to buy it.