You would be very wise to take everyones advice and get a Tip Top Mantis. You'll thank yourself as your module collection grows... BUT... Personally, I enjoy creating individual "instruments" from smaller cases, so I took a run at what I think would be a fun little 84hp inside the NiftyCase
PICO Seq is a surprising little sequencer. Pam's for all sorts of clocks and timed modulations. Plaits because authentic Mutable Instruments are the best (boo Uli). Forbidden Planet from your original build, but I like Lugia's MMM filter choice better. Maths because Maths isn't too complicated. Veils VCA as suggested above. Beads for granular and reverb. PICO DSP for another layer of FX. Mixup to finish everything off
To hit your 1500 Euro budget most modules can wait since you're planning to sequence (and presumably record / add effects) with Ableton. A great start would be: Plaits, Pam's and Maths, then add modules as you learn what you need