Quality 1-pc 40" or 46" clearing rod (Bore Tech, Tipton, Dewey, etc)
Bore Guide
6.5mm bore brushes
6.5mm jag
6.5mm bore mop (optional but recommended)
Bag of patches
Your choice of bore cleaner and copper solvent

I don't recommend buying a "kit" as usually they're far from being high quality. Get yourself a small to medium fishing tackle box to put all of your cleaning stuff in (except the cleaning rods of course). For the cleaning rod(s) you can buy a pre-made case like this one, or you can make your own out of PVC as shown here.

FOr cleaning rod length I generally just match the overall length of the rifle (muzzle to rear of butt pad) as close as possible. Nothing worse than buying a cleaning rod only to have it show up and find it's a few inches short of what you need.

I generally don't take my cleaning stuff to the range with me because rarely do I ever shoot the same rifle enough in one trip that would warrant having to stop to clean it. Instead I just clean my firearms when I get home before putting them away. As such I just have a rack that my cleaning rods hang from in my workshop since I'm not dragging them to the range. I do however keep a 3-pc .22cal aluminum cleaning rod in my range box just in case I need something to free up a stuck case in the chamber.