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I'm not that familiar with the Mutamix, but I don't think it operates as a traditional VCA. It looks like there is only CV control over channel muting, not over channel levels. You almost certainly would want something that serves as a combo VCA and mixer like the Intellijel Quad VCA, Veils, or the Zlob Vnicursal. You have also included two delay modules which seems a little redundant, but I'm not sure what you are trying to accomplish sound wise, so that's up to you.
A few more things to consider: Do you really need Data in your setup? It eats up a LOT of hp for what it does. I know Data looks cool, but is it going to be indispensable for you? I would recommend against it in a small first rack.
I know a lot of people love the Frap Tools stuff, but I find their interfaces confusing and unintuitive. As a beginner, might you be better served and more productive with something a little more straightforward like Batumi and Zadar for your modulation sources? Maths may be a better option here too.
Finally, there doesn't appear to me to be much rhyme or reason to the layout or signal flow in your rack. I would start by grouping oscillators/sound sources together, sequencing/clocks, modulation sources, effects, VCAs and I/O, etc. As it is, your rack looks really jumbled. Think in terms of an old school hardware synth's signal flow.
You didn't mention what type of music/sound you are interested in making, so it's hard to tell if the modules you have chosen will help you get there. Plaits is a decent choice for someone new to modular because you get a taste of many different sounds, and I know a lot of folks love the sort of aggressive digital sound of the Hertz Donut. Let us know what you are hoping to accomplish, and we can probably make some more specific recommendations.
Have fun and good luck!