Well, you definitely should check what is played around you, because commander and highlander formats don’t usually have the wide support that other formats have – don’t expect regular events for example, or tournaments. Most EDH is played in groups of people knowing each other or as a side event at FNM. Spending 1500€ into a deck you don’t get to play because there is nothing happening in your area of the world you live would be a bummer.
cEDH follows the same rules and banlist as EDH, but has a totally cut throat mindset. It still is multiplayer, but it is the place of EDH where – after clarifying that you all are set up for cEDH, of course – you don’t have to listen to complaints about comboing off turn 2. EDH – despite following exactly the same rules – is casually oriented and the more formal “kitchen table” magic. So you definitely need to check with a play group what power level they run, because a cEDH deck will be pubstomping people and that means you again don’t get to play your deck, because you won’t be invited back. Casual EDH has something worse than rotation: it has these guys called “other players” that just don’t play with you if your deck isn’t matching their power level expectations, and then your money is just wasted.
Since you talk about €, CanLander probably is out, as that is mostly played in areas of US and Canada, and not many playgroups exist outside that. I know that in Germany – at least where I live – you can find places to play Dual Commander and you can find German Highlander (this one probably mostly because it was invented here 😉 ). Normal EDH is the format most widely spread, but that’s casual EDH, not competetive. For cEDH you have to expect to travel to other cities if you are lucky to even find other competetive players.
And now for something potentially unpopular in this sub: If you really look for a normal competetive constructed format you get a chance to play regularily and have the money to spend, go for Modern or Legacy. There still is ok’ish support for Legacy in game stores and events, even though Wizards is dropping the ball on Legacy quite a bit lately, and it is an eternal format without rotation and a moderately small banlist. And Modern just is thriving and well.
Reason for my suggestion: it’s the closest to what you are used to, it’s unencumbered by “casual politics” and if you have 1500€, you can definitely buy into a solid deck choice. Modern decks are usually around 1K€, so you should be golden there, Legacy decks are a bit higher, but you can start with decks that can be budgeted in the land base and work up from there.
Especially cEDH is far from cheap, my cEDH decks are alll way above 1k€ and the better ones easily can go above 3k€, because you often go 4 or 5 colors and the land base with duals and stuff eats up your budget. And even if you go for mono colored decks there, the fast mana and efficient counterspells eat tons of your budget, too. But all that is moot anyway if you don’t have a place to play it.