I'm 55 and I just started park last year (except for a bit of experimentation the year before). Along the lines of what Snowolf said about deliberate and considered progression, body armour is a must. I've got knee/shin pads, impact shorts, and a spine protector. And a helmet of course. You don't have to always wear all the shit, as slyder says, but definitely wear it when you're hitting the features.
Hey Donutz: I am sure you probably researched the crap out of body armour before you pulled the trigger. What company did you go with? And by the way....55.....you just made my year!!