Garden Simulator is nice and relaxing, buut... there's really not that much to it. Which isn't surprising considering the title, but it's definitely not worth it at full price. Even at a sale, I'm not sure unless it's a massive sale, as there's better games to spend your money on.
From an achievement hunting standpoint: I have 8 hours played as I wanted to go for full achievement completion, but to be fair, you'll have seen everything once you're about 2 or 3 hours in. The rest of the time is just a big grind.
HOWEVER, if you want to play it just to relax and decorate your virtual garden, you will get more hours of enjoyment out of it. But even then - I just don't think it's worth it for this price. The gardens designed in the trailer look really nice, but there's not a lot of decoration options in this game, so you'll run out of ways to redesign your garden pretty quickly as well.
The graphics are nice though, and the cat is cute.
It would be worth it for like €3 - €4 in a sale, and around that price I would recommend the game, but not for more than that.