don't skimp on case or power, especially if you find modules to be expensive - the case protects them and the power gives them life!
if it was me I would next want a better modulation source (I like Maths as a first modulation source*) and some basic utilities next (links, kinks, shades or similar functionality in different modules - wmd/ssf toolbox for example goes a long way to covering a lot of basic utilities) and then possibly a stereo mixer - before adding any more sound sources or modifiers
I've looked over your first response as I've made some changes over the past week. Seeing similar builds has led me to make some adjustments. I would love to hear your thoughts on the changes:
Case: Considering power, size, reliability, etc., and cost, I'm probably going to go with a 6U 84HP Doepfer low cost case. I'll message the Case From Lake owner as well. As much as I want a custom pretty case with polished walnut wood, etc., the LC6 seems to be a steady workhorse and solid choice for a first case. Plus, the extra money in my pocket can go towards some utility modules.
Modulation: I've added Maths and Pam's for some modulation and extra clock sources.
Utility: Following your advice on utility, I've added MI's links, kinks, and shades. I've also seen these utility modules echoed in other posts here and on r/modular for builds that are similar to mine.
Stereo Mixer: Since I'll eventually have Beads and Arbhar, two stereo modules, any recommendation on a stereo mixer? Will I need something that has multiple stereo ins / 2 outs? It's hard to make sense of what would work with my build, or what's overkill for my sound sources. There's so many choices. Beyond that, it looks like I'll still have a little room to spare for additions down the road. Thanks in advance!