Mad rock R3 is an amazing pad!!! I just used it today to protect some less than level landings that would've been very hard to protect with stiff foam. It has ridged sections that allow it to bend very easily over rocks and awkward terrain. Not the biggest surface area in the world, but big enough you could use it on its own (obviously best with a spotter).
I've always been good with that and another more firm pad - the classics mentioned above that have 2 sections of hard foam. (I don't do many crazy boulders). It's rare that I want more than 2 crash pads if I have a spotter to move stuff around. If you're just getting started you'll probs be fine with one and combining with friends.
I will mention that if you are in a college town, they often rent bouldering pads from the University gear rental shop. That's what I do to supplement my R3 when I don't have friends with pads to climb with.
I much prefer having a more flexible and niche pad, since people you climb with are more likely to have a traditional version that will complement it.
I have an Organic pad and I like it, but my friend has an Asana pad that really impressed me. The foam feels the same as organic and it’s also made in the USA, but the Asana has better buckles and closures.
IMO the biggest difference from one pad to the next is the buckles and straps.
I make do with one gigantic 6 ft. by 4 ft. pad: Metolius Magnum. It's the surface area of two standard pads. Metolius doesn't have as good foam as the organic, but Organic doesn't make anything that large. I like it cause it's a single crash-pad solution, I don't need anything else for a good chunk of boulder problems out there I'd be willing to solo. And for the harder ones where it's either high-bally or wandery, you'd most likely have other people with their own pads.
And, since it's 6 feet long, you can use it to sleep and stretch on. It's tri-fold so it doesn't take up too much space folded, but still a lot -- you'll want a decent-sized vehicle to transport it. Or, just chuck it on the roof.