I'm a noob myself, but on a similar path / starting point so thought I would chime in. I wanted to build a modular system to get a lot of standard vintage lead and bass sounds and have a lot of control, but then also get really crazy with heavily modulated / textural sounds too.
Of the above rack, I have the Mother 32 and the Blue Lantern Looping Envelope so far, and the rest is just a bare bones plan for future purchases. For lead sounds, having a true fully adjustable ADSR gives you more control than the limited envelope generator the M32 has. Plus, since I want to do some ambient / layered / textural stuff, having a looping envelope with CV input free to modulate things other than the VCA will definitely come in handy.
A second utility VCO, with sine and triangle waves, gives waveforms the M32 doesn't have already. A clean sine wave is often the starting point for ambient sounds.
A "pluck" sound source like Mutable Instruments Rings, or the 2HP Pluck is a popular sound that works well in rhythmic ambient stuff.
The Tides is on my list mainly for the variety of LFO waveforms possible, since it can help create some slow, evolving modulated patches, though there are tons of LFOs to choose from, many with CV control.
Some variant of Clouds is a definite for my planned rack, to mangle and stretch sounds.
Effects like delay and reverb are important if you want to go down the ambient road. I don't have any here because I have that all outboard already.
I actually had a Korg Minilogue and sold it to help fund starting a Modular. Most of the stuff it did that I liked, like brassy pad sounds, can be done so easily in a softsynth like Korg's Mono/Poly vst that's available for $50. I don't miss it that much, especially for leads and arpeggios.