A random comment about getting into modular that I think is cool.

NOTE: THIS IS NOT BY ME. Source is at the bottom of the page.

"If you're thinking about going modular but don't know where to start, here's some advice! Idk if this is gonna be at all helpful, but if my personal experience is helpful to at least one person it'll have been worth typing. FYI: I'm not an expert, but I am quite familiar with this stuff, and I had to do it on the cheap, so if you're in a similar boat, maybe this can help.

There's a really bad catch-22 here: You absolutely need a plan for your modular before you start building it, or you'll waste a lot of time and money before you find a system that's right for you. But you can't possibly make a plan until you've spent kind of a long time using a modular synth and getting to know them. Unless you're fortunate enough to have a friend who already has a modular you can try out, here's how I would approach this dilemma:

I started by splurging a little on my first oscillator, and then buying a few other much cheaper modules to make a functional system. I spent a few months getting used to this system and learning what I liked and what I didn't. With that experience I was able to make a plan for my system and start slowly replacing the cheap modules I didn't like as much with the bigger, cooler ones I was excited about. Here's what I'd advise starting with if you want to approach it this way:

Find an oscillator / sound source module that you think sounds fuckin rad. This is the only module you need to splurge on at this point. If you don't love the way your oscillator sounds, you'll have no fun at all. I started with Plaits by Mutable Instruments, and it's still in my case today.
The rest of the modules you get at this stage can be cheap and simple. You just need enough modules to have usable system, and you can replace them with modules you love later. (unless you can afford to swallow the whole cost at once) You can resell them on reverb.com if you don't end up keeping them. If you buy them on reverb in the first place, you can even get all your money back. You'll need.....
At least one or two cv sources. You just need enough cv generation to get your system up and running. Consider which cv inputs on your oscillator you're most eager to plug into, and how you'd want to control them. Common types include LFOs, Envelopes, random sources, and sequencers. Consider if you want your cv to be fast, slow, predictable, random, simple, complex, etc.
VCAs. You'll need at least one of these to control the volume of your oscillator (unless that oscillator has some kind of built in volume control). You may also want multiple VCAs so you can control the amplitude of your cv with other cv. There are a lot of modules which have multiple VCAs all in one, and they're usually cheaper and more space efficient than buying multiple individual modules.
Audio Output. Eurorack runs incredible hot so that audio and cv signals occupy the same voltage range, and are thus interchangeable. But this means you need some way to reduce your volume down to line level before you send it out to your speakers/mixer/audio interface/headphones/etc. Some more expensive cases have audio outputs built in, but your starting case probably won't. In that case, you need an attenuator to lower the signal. There are also dedicated audio i/o modules, but you don't need to worry about those yet. Remember that this attenuator output will be 1/8" mono, so you'll need a 1/8" to 1/4" cable to record your stuff, and a mono to stereo adapter if you want to use headphones.

You now have a funtional system for as cheap as possible (minus the oscillator), which is unfortunately still kinda expensive. But once you're familiar with this system you'll be able to think about all your possibilities more concretely, and once you have a real sense for it you can start expanding / replacing modules.

Some final tips:

Before you buy a single module, make sure everything you've got your eyes on will work together. Some modules need certain inputs to operate at all -- for example, envelopes and sequencers will probably require a trigger or gate signal from somewhere. If you don't want to get into triggers and gates yet, find envelopes with a built in trigger button, and sequencers with a built in clock. Imagine precisely how you might patch your system, and make sure it all fits together. If you're not sure about it, take your plans in to a synth shop, or ask somebody who's modular-literate, and they can tell you if your system plan is functional.
AVOID MUFFWIGGLER AND GEARSLUTZ AT ALL COSTS. If you've never heard of those, they're the two most prominent modular forums online, and yes, those are their real names. They're also terrible. People on there will tell you that they know exactly what's best for you, and they will curse you out if you disagree. They also tend to only value the opinions of old white dudes. Sometimes they're useful for specific info, and obviously not everyone on there is shitty, but when you're just starting out, they'll probably just lead you astray.
You DO NOT need a Maths. Maths by Make Noise is the most popular eurorack module of all time, and it is genuinely incredible. But many, many people will tell you that every eurorack system literally needs to have a Maths in it, and that's just not true. It's pretty expensive, and for a lot of systems it's not worth it. The Maths cult is irrational. But if you can afford it and want it, it's a great module. Certainly look into it, but think for yourself.
Precise pitch is not a given. Most cv sources don't produce precise musical pitches. That might not be important to you at this stage, but if it is, look into pitch sequencers and quantizers. Precise rhythm is also not a given, and for that you'll need a trigger sequencer.
If you have midi controllers, look into midi to cv modules. They're a great way of getting control over your modular with gear you already have and using it like any other synth in your setup. They also provide triggers/gates and precise musical pitches.

And finally, there's really no right way to approach this at all. I find this to be the most beginner-friendly way of approaching modular, but something else might work way better for you. Good luck and have fun!"

Noah Giom, May 2020 - original comment here