Poked around online since I wasn't familiar with the product in question, and only notable point I came away with was "“Eco” in Ecostop stands for Economic, which this stop bath certainly is."
Prices don't look overly outlandish, but I'm not super familiar with markets over in Europe. If you're planning on being more environmentally friendly, then I'm not sure what to say beyond follow proper protocol on disposal, especially on your fixer.
Biggest thing is that once you settle on a combination that you can reliably get locally, try to stick with it for awhile till you're nailing your consistency, and your negatives/prints are coming out exactly as you expect even if that means they're coming out with some trait you actually don't like.
Once you can reliably reproduce all of the specific traits in your images, then you can begin the process of adjusting things to dial in the traits you like and avoid the ones you dislike. Photo chemistry is a blend of art and science, but early on it can be easy to dive down a frustrating road of chasing your own tail trying to fix problems before you're able to reliably identify the source of the problem.
You don't need to be pushing science and treating it like you're a chemist after a Nobel prize in understanding every last low level detail, but at least keep your processes consistent from batch to batch, and only make changes for very deliberate reasons.
You're going to find a lot of different camps suggesting you join them with their favourite. And to make things fun for you, not a lot of photographers are great at explaining why they're in a given camp... So you kind of have to read between the lines and look at photographers images. Read up on reviews and look specifically for commentary on why someone is using a given option or process.
That said I typically use Ilford ID-11/Kodak D-76, which ever is cheaper when I go to restock, for no other reason that it is a popular baseline option that is inexpensive and easy to use. Normally go 1:1 one shot developer, with indicator stop bath, and Ilford's rapid fixer.
The powder packs last basically forever if you're storing them halfway sensibly, and the mixed concentrate can sit in a bottle in the dark for several months if you mix some up and don't get around to using it. [I like to break mine down into pre-measured bottles if I have excess left over from a session. It does have a drawback of being advisable to let sit at least over night after mixing before use...]
You can technically get lower cost for higher volumes with some of the other developers, but you're then at risk of lower consistency or having to toss unused chemistry if you're not keeping up with volumes.