Looking through that page, the F450 FlameWheel style kits are still available, and a reasonable choice for a DIY Ardupilot drone. These are about twice the size of a typical FPV quad and will give you more room for sensors and/or a gimbaled camera. Alternately, if you think everything you want will fit on a 250mm FPV frame (they can carry GPS and a fixed GoPro), there are lots of cheap components due to the popularity of FPV.
I would agree with the advice to also buy a cheap toy quad to learn the reflexes you need to fly, and for when your friends want to try flying. They're so cheap now that it's a tiny fraction of the cost of a bigger multi-copter. You won't find any running Ardupilot though, as the flight controllers are too expensive.
The Hubsan X4 H107 is still available - watch out for the different versions, there's a basic version, one with a recording-only camera (that's a bit pointless) and an expensive one with a low quality FPV camera.
The Blade nano has been replaced by the Inductrix - they're quite expensive but their customer service is good.
Eachine's range of toy quads are pretty good and very cheap. The E010 or E011 both work well and can often be found for $10-15. The E012 is smaller but only flies for a minute or two. The protected props make them strong enough for beginners to learn to fly indoors, but they can be flown outdoors in light winds. I would suggest ordering a few spare batteries - one is never enough.
Some of Eachine's range (like the E016) have altitude-hold, which seems like a great idea, as holding a constant altitude is one of the first challenges to learning to fly (especially indoors) - however I've found these need extra trimming to hover accurately and really aren't suitable for a beginner unless you've got an experienced helper to trim it each flight.
