Perhaps add Korg Minilogue or Monologue to the list? Both great affordable synthesizers and fairly portable.
Novation Circuit is the one that stands out from the rest being a small combination of synth, sampler, drum machine and sequencer. Almost a little workstation.
I think you need to define a little bit more what you want to be able to do with the synth/workstation? Since Volca FM, MicroMonsta and Circuit are all very different type of synths. All three are very fun and fairly easy to use.
I have a collection of synthesizers. Everything from old analogues such as Yamaha CS-5 to more modern synths like the MiniBrute, Reface CS and so forth.
So I’d say it depends a lot on what you want to be able to do with your first synth.