Well, before pulling the trigger on some of RS's stuff, you might consider snagging a Kilpatrick Phenol. Less expensive, to start with...plus the working paradigm there is right out of the Serge playbook: all bananas, no separate signal paths, and it'll connect perfectly to actual Serge, RS, Elby, etc, in addition to Eurorack provided you use an adapter module/box and establish that ground. Bananaland is a bit of a different take from "typical" modular, and the Phenol would be a perfect intro...plus it's got plenty of useful features that'll play nice with any Serge-ish additions.