Jim is once again spot on, you need a bigger rack. Eurorack requires lots of space as these single use modules take up space and you need a lot of them to get the most out of your investment. If you buy a small case because the bigger cases are too expensive you are setting yourself up for disappointment.
There are lots of cool videos of small racks sounding awesome, the issue is that these small racks sound awesome for that specific sound and in some cases only that kind of patch and without enough supporting modules you will get bored or frustrated rather quickly. Ultimately either reselling your modules or getting a bigger rack that you should have started with.
It would be in your best interest to start with a bigger rack (don't focus on the need to fill it right away) so you have the best chance of finding your way in eurorack. It is an expensive hobby and there are lots of other ways to try a little before making this kind of investment like a neutron, dfam or similar semi-modular system to start.
I also wouldn't start with the Ataraxic (I have this one) as a voice, this is apologetically digital and taming it into warmer tones takes a fair bit of work. I would start with something like the Dixie II (my favorite workhorse osc), or similar analog osc. I like the Dixie because it has a ton of features at a great price, you will get a lot more mileage out of the Dixie as a first osc imho.