As you're living in Europe you may get Chosera and Naniwa stones much cheaper than our American friends at Edenwebshops.
My suggestion would be to get a relatively coarse stone as well. You will need it whenever you will want to adapt the edge to your wishes, especially in the case of the Aogami Super steel. I use 400, 800 and 3000 Choseras. Regards.
I have ordered bester and chosera stones from dieter Schmidt in Germany and they arrived quickly, being Europe no import duty as well, Dictum tools also in Germany have a good range of stones. If you want king stones they were on sale at greenman bushcraft in the UK but that was a few months ago. I'll check later today and post some links.
In terms of progression I'd go for a 1k and 4k or a 1k/6k combo stone plus a piece of leather to strop the edge on