You have an oscillator, a filter, and a VCA. The Maths can pull duties as a envelope generator, but basically a very simple one in most cases.
How do you intend to control the pitch of the oscillator and trigger the envelope generator to then control the VCA? How do you intend on hearing the output? What about modulation of some of the CV inputs throughout the system?
The power of Eurorack lies in the modulation opportunities and being able to build complex chains of modulation to get something unique. For the amount of money that you're spending for the basics here, you can buy an entire synth voice in Eurorack or a semi-modular synth that's Eurorack compatible for a lot less money and with a lot more features. If you do a search on Synth-Voice in the module section, you'll have tons of options to get yourself going. The Manther looks pretty tasty to me. Take the money that you save and buy some sort of sequencer, effects, and some other useful modules. A proper synth voice will stay useful no matter how large your system grows. Sometimes it's a lot more convenient than patching up a basic sound if that's what you need.