When it comes to the boots, what all those mean is basically nothing on the boot. No strap belts (they are on the back of these boots
https://www.tradesy.com/i/merona-black- ... /25790504/), no stretchy bits (you can see the stretchy bit on this shoe
https://www.pinterest.com.au/pin/600667669029144786/), NO ZIPS, look closely at the boots and read the description of the product to see if they have zips, hidden or otherwise you can not have ANY ZIPS for cert 3. When it comes to decoration on boots this is usually fancy stitching or patterns, so you need to avoid boots with company logos or other stitching that is there just for show, but English Riding Boots usually don't have things like these anyway. A conservative heel means a heel most likely under 1.5 inches high, closer to 1 inch. So no boots like this (
https://www.shiekh.com/fashion/shiekh-w ... black.html)
, something with a heel closer to the ground (
https://www.blundstone.com/shop/black-l ... style-1901). Essentially, you are looking for a tube of leather with a shoe on the bottom that you can fit your leg in. This page on Etsy has a few that I would say pass cert 3
https://www.etsy.com/au/market/english_riding_boots , Ebay has a few too
https://www.ebay.com.au/b/Leather-Tall- ... n_60631889 . Otherwise you'll have to modify a pair, taking off the strap if it has one, etc. You could check out some domestic costuming shops, online and offline to see if they have leather boots. Once again, don't stress too much, the only thing that is making your search difficult is the fact that you cant have zippers, as most boots do because they are made by sane people.
As for the gloves from leathermystics, I would say they pass cert 3. The cert 3 requirement that they have a flair out towards the forearm is incredibly common in cosplay or swordfighting gloves. In fact, it seems all of leather mystics gloves seem to have this flair.
As for the imgur link, it's to give to someone who can sew your robes to give them an idea of what you need, but I'd do a better drawing before showing them I just did that on Paint
And that forum link took you to the Attack Of The Clones Royal Guard forum, just for convenience, should you delve into that forum to find the base robe pattern for your robe, and just more information in general. After you find the robe pattern, then you'll have to change it slightly to make it a shadowguard robe. This is the holy grail of the AOTC royal guard
https://vignette.wikia.nocookie.net/sta ... 1101141053 . You will have to line your robe with a material similar to your undersuit. To make it shadowguard, I think you just have to have the back robe split from the bottom down the middle until a few inches below your neck. Once again, don't stress, just do some googling or ask some questions to a seamstress or someone you know who can sew to gain some knowledge on the subject. Velvet or velveteen for the robe, although if you're going for shiny armour silk velvet will probably suit you, very fancy-looking.
Some photos of the AOTC royal guard robe that yours will be based off of (just click on Photobucket photos to clear them):
https://www.forcepike.net/forum/viewtop ... =26&t=1977
https://www.forcepike.net/forum/viewtop ... 0&start=10