armor on a budget

I guess I'm mostly an XC rider, maybe an "agressive" XC rider. But I'd like to start doing more of the freeride and DH trails around here, though I might need some pads, so looking for advice on:

Which pads do people consider most important? Is just knee/shin pads ok? elbow knee guards too?

What are the best pads for cheap?

Right now I have some sixsixone knee/shin guards I bought a few years back, but I think they are junior sized cause they say "Large" yet they don't fit well on my small/medium sized body: too tight, uncomfortable, slip down, etc. Looking to sell em and buy something that fits better, but is cheep.