Others will probably jump in here, but you'll need a good quality pick, that's not too heavy; an all plastic nugget scoop or inexpensive, small gardening shovel; a magnet on an extension wand or a magnet that's secured directly to your pick's head in some fashion; a plastic bottle with a screw-on or snap-on lid for your nuggets; some quality headphones for your detector so you can hear the tiny whispers and subtle changes in your threshold; insect repellent if you're in an area with bugs; a pouch for trash; a utility loop to hang your pick on when you're hiking back out.
A 100 oz hydro pack ! With enough room to carry essentials like medical tape, wallet,keys,knee pads,cell phone,screwdriver or crevace tool. A scoop and a good pick with magnet attached
Small back pack with all the above plus add in a chisel and hammer and gloves if you are going to be around hard pack or caliche.
Depending on the area I also carry a sidearm. Also a fanny pack to keep certain things handy. Oh, and knee pads.