For a scandi grind knife not much compares to Japanese waterstones. Most waterstones will do fine but with D2 as the primary steel I would be looking to something better than the average King stone.
At the top of the list is the Naniwa Professional, previously known as the Naniwa Chosera, they are some of the highest quality stones on the market with their defining feature being grit control. These stones are known to produce the cleanest and most consistent scratch pattern of any stone. The only down side is cost, a set of 400, 1000, and 3000 stones would run around $300. These stones are usually my first pick when sharpening Scandi grinds.
Next we have Shapton stones. These are my favorite because they get sh#$ done and produce very sharp edges quickly. These stones are fast cutting hard ceramic stones, they cut faster than most other waterstones are are ideal for very hard or wear resistant steels. The sharp ceramic abrasive is rated in Mesh and not Grit like most stones, this means that the scratch pattern is a bit coarser for the given grit and even at finer grits the polish has a scratchy appearance. You still get a finely polished edge but when compared to other stones you can see the slight difference. Lots of stone set options from this brand, on sale now is the 500, 2k, 16k Glass stone set from CKTG, really good deal because the 16k is $150 by itself and you get the whole kit with stone holder for $214.
For the Shapton pro line I would recommend the 1k, 2k, and 5k. These are often preferred to the Glass stones because they have better feedback and are a bit more aggressive on the low end. The Glass stones have a very slick feel and almost no feedback, often described as robotic or dead feeling. This is the main reason the Pro have a greater following than the Glass stones.
All the above stones are splash-n-go type stones of the highest quality and would be my first recommendation. If budget is a concern then some of the more common stones that require soaking in water might be best. The King Deluxe 1000 is a classic stone with great sharpening feel and despite being called slow it can sharpen rather fast, although it does wear down quickly requiring constant lapping. You could follow this with a Naniwa 2k Green brick and have a great two stone combo. The GB is just as soft as the King though so the stone is easily gouged if your technique is off. This can be viewed as a teaching aid or a roadblock in learning, depends a lot on the individual at that point. I like them despite their soft fast wearing nature because they work well and can produce quality edges.
So there's a little intro to a small but quality selection of stones and info to get you started. To better help us help you, let us know your budget and possibly any other cutlery you may have to sharpen.
