I can only see modules on the right.
-- abstractrhythms

Same here.

Context: Pairing with some outboard synths (Digitone, Digitakt), had initially planned to sequence and clock from the Digitakt.
-- toiletfingers

What do you hope this setup will achieve, supplement the existing gear with modulation (you'd need a CV to MIDI converter, most likely), create a completevoice with Plaits, something else I'm not seeing ? What do you mean by initially planned, did that change and if so, why ?

I have about $500 to spend before I have to pump the brakes for awhile, trying to figure out what makes the most sense to gain maximum enjoyment from my case until I can afford to further expand.

I know I need a filter, an envelope, really attracted to Pam's because it does quite a bit that I think would bring the rest of the case to life. Rings is also attractive to me but I know there are other things I would probably benefit from acquiring first.
-- toiletfingers

Most likely not the answer you're expecting but I'd say that with that kind of cash, I'd probably be looking at an Analog Four Mk1 in 2nd hand, a very capable 4 voice analog synth, with the sequencing paradigm you already know from the Digitone and CV outs too if you want to integrate that with Eurorack... Now if you already have some modular gear and you're only looking for a filter + EG with a $500 budget, maybe the Intellijel offering could be interesting, say a Quadrax and a Polaris in 2nd hand ?
Also, what do you hope Pam's or Rings would bring to your setup ?

I feel like there's just not enough we know about what you want to do to be able to answer efficiently...

--- Voltage control all the things ---