I started with a MicroBrute, and now have one M32 and another on the way, supplemented by some modules for utilities and more timbres. My goal is to have a nice hardware mono synth based around the Moog sound and filter. I've owned other modules but am downsizing - although I've tried various filters and oscillators, I always came back to the M32 filter because it sounds absolutely fantastic, as do the oscillators!
If you put a bit of time in to learn the sequencer, it's not too slow either, and is very powerful for the price of the M32! If I really want to jot down a sequence asap, I use the insanely easy MicroBrute sequencer.
If you still use Ableton, I recommend looking at a MicroBrute as a controller - you get a small keyboard, pitch and mod wheels, an LFO that syncs to Ableton's tempo (not many LFOs actually sync in eurorack), and of course the extra envelope, waveforms with various timbre shaping, and the nice little sequencer. It's cheap as heck too, I got one for under £150 on eBay.
If you want to get individual modules, buy them secondhand, look after them, and if you don't like them, sell them on modulargrid or muffwiggler for the same price, so that you break even or lose only a tiny bit of money. It's worth the journey and you will never end up with what you thought you needed.
Just my 2 cents!