Nylon is great. Pound for pound its the warmest thing to bring along.  Cheap nylon running pants (unlined) and a windbreaker will serve you well.

For the spring . summer you still want to have insulating layers.  I bring along a complete set of long underwear and a light pile top.  Plus a light pile hat.  You should be able to put everything on over each other and still move easily -- including topping off your layers with your nylon wind gear.

Hiking boots are a must.  I prefer the all-leather variety.  (But I hike a lot).  Make sure you have put some sort of sealant on your boots so they don't leak.

Water -- 2 quarts -- and food should go without saying.  Plus sunscreen and bug repellent.  (I usually coat myself with sunscreen after I show the morning of a hike and leave the sunscreen in the car).  I also don't bring extra socks -- I figure I can suck it up for a few hours if my socks do get wet -- which they don't because I have sealed my boots -- and I wear a pair of gaitors to keep the mud , dirt and rain out.

And speaking of rain -- don't forget rain gear!