I started last spring so I'll give you my observations based upon doing some things either wrong or perhaps in the "wrong" order.
Jacket - started with a Marine shooting coat - padding in the right areas but no rubber non-slip on the left elbow/rib area, also, not that tight. Step up was to a Champions 'cheapie' canvas with adjustable closures and good rubber in the right places. Champions and Creedmoor both have an offering around $70 - 80 bucks that's a great starter. Wasn't willing to spring for a leather hardback w/o more experience and a personal fitting. BTW, the canvas by all the makers seem to run small ... I'm a 42 tall in a regular suit but a 44 jacket just fits.
Scope stand ... tried the old binoculars for 200 and 300 for about a month - that's hard on the neck in prone and really screws with your position. Got a stand (Ray-Vin, stainless, 1 inch, 1 hand scope adjustment) and feel it's a great investment.
Scope - now making do with a junker that just barely works for 300 yds. You're not looking for holes - just mirage at 300 - 600. Either wait until you can afford a Kowa with the long eye relief (not the zoom, the LER) or go with a Konus 20-60*60 for the short term...you'll eventually end up with a Kowa if you stick w the sport. 60 or 66 models are more than adequate, the 80s are overkill ($$$)
Shooting glove - mostly used to tame pulse as well as enhance comfort ... until my positions get a lot better, pulse is not an issue. Quite happy with a mechanics padded glove with some rubber on the palm - probably $8.
Sling - got a Les Tam and a Turner (had them already) ... great once broken in, but they take awhile. Have mostly used a GI cotton web sling and actually prefer it - you need a real cotton model, not the nylon repros that stretch.
Stool / Cart ... depends on the ranges you frequent. If it's a long way from the parking to the line or if you walk between the yardage lines, a cart is worth it. I got a Schneller used - $500 new, not quite worth that but real nice. Takes up 1/2 the back of an SUV though. A lot of guys make their own from a 3 wheel baby stroller or a hand cart + a little ingenuity.
For just a stool, Creedmoor has a nice one with a huge capacity bag. Way less expensive is a Walmart mailorder camp stool that comes with a bag attached beneath ... $14 or so. I still use the plain stool for informal matches, offhand or walk'n'paste when the cart is just too much hassle. Also nice in the pits while waiting between strings.
Earplugs plus muffs, especially if you get set next to a couple 30 cal. The slimline muffs shotgunners use are nice as they interfere with cheek weld less.
Personal preference - I use a flipdown plastic eyeblock so that I can shoot with both eyes open - really helps with the eye fatigue.
Mat - started with a chunk of carpet - works fine, a little elbow burn as you move around. Catch the Midway shooting mat on sale - $20, very well worth it, wouldn't pay any more than that for a 'name' brand.
5, 20 round straight body mags. 1 for single loading in slow, 4 holding 5 each (or 2 and 8) for 20 round rapid stages. Never found a need for the official Bob Sled type single loader ($40) - just pop them in with a pinkie on top of a regular mag follower and drop the bolt.
Case deflector - only use in slowfire ... keeps the brass in a neater pile, not worth the chance of a bounceback in rapids.
Baseball style cap - some like the ones with "sides" on them to block errant cases from your neighbor,
needle type oiler,
color coded ammo boxes for short vs long line rounds,
empty chamber indicator,
highneck or hooded sweatshirt for under the shooting jacket - keeps your neighbor's empties out of your shirt - a hot '06 case down your back can really play havoc with your concentration in prone rapid.
I usually have a small tool kit in the car - case extractor, range rod, front sight tool, misc, etc.
There are a bunch of great stickies and articles as well as fairly frequent sale items on the Nat'l Match forum ...
http://www.usrifleteams.com/forums/index.php?act=idx
Enjoy!
/Bryan