I bought a pair of TLD 5450's last summer and have liked them a lot. Biggest thing is to go down at least one size possibly 2 to get the right fit. For reference a pair of XL TLD T-bone knee pads were still to tight when I tried them on. A pair of medium 5450's fit just right. Very light and perfect for long rides, I don't even notice them.
I use the fox launch pro elbow pads (light) and some 661 knee/shin guards. Believe me you'll want to them wear the one time ya don't you'll end up like me. Breakin both of your elbows and suffer a concussion and remembering none of it.
I use troy lee eg 5550 elbow/forearm guards. They fit me pretty good and don't slide around. They offer decent protection from sliding injuries and light impacts. Last summer I took a good digger from about a 6 foot drop where I fell on my forearm and got a bursitis on my elbow, so they aren't exactly bullet proof. But if I wasn't wearing them a lot more damage would have been done. They are also pretty compact and fit well in a pack.
I don't wear anything but a helmet. I ride the same trails every day, I know where everything is and nothing sneaks up on me. Only time I wrecked up there was when I did it on my bmx bike. Damn 20 inch wheels don't get over rocks as well as mtb. I still made a pretty good time though.
On the occasional chance that I do go somewhere new, I wear a full face and shin guards. But no elbow pads.
I wish I could just wear and a helmet and be done with it but I can't do that.
I ended up removing the shoulder cups on my Dainese jacket (I might even unstitch the shoulder padding altogether), makes things less bulky. The important stuff for me is the spine protector and elbows/forearms.