I would have a look on second hand Dreadbox, Erebus or Nyx which are both analog, semi Modular’s, and represents a nice start into synthesis! You will be able to sample and resample it with the DT II…
If you go for the Digitakt 2, keep your sample pool tightly curated. You don’t need 500 snares or kicks. Choose 20 - 30 of each type of sound and you’ll be golden.
As mentioned, the Digitone MKI is a fantastic FM groovebox and is at the moment maybe the best value on the used market. I saw one for 350€ recently. It may not be perfectly suited for your style (acid, psytrance), but certainly you can make some kind of this sounds with a bit of deeper tweaking. My advice: Look out for a Virus C. With a bit of luck, you can find one between 600-700€. The “C” model has integrated effects and up to 16-part multitimbrality and enough voices to run a bassline, lead, and more. Very well suited for all kinds of techno like acid and minimal, and heavily used for years in psytrance. The DT2 with its 16 tracks can sequence it perfectly and you can route/mix into the DT2 inputs. Full tracks and knobby synth action with that setup would be ace.