modular has been a productive thing for me. there’s a lot i really love about it. it took a bit to get there but i’ve no regrets really.
other than the advice above i’d say think hard about what you want it for and have a plan. do a lot of research. if there’s a modular store within driving distance that has demo systems make a couple trips and spend some time patching. if not then muffwiggler forum and youtube are your friends. check the sites of the manufacturers you’re interested in. download manuals etc.
for me modular excels at complex monosynth stuff and sound design and multitimbral operation with complex sequencing. but you can bang our any kind of thing on a modular once you know your way around.
don’t overlook digital modules. there’s so many really great things that are digital. i wouldn’t go all macro programmable with modules… too many things with multifunction button presses and screens etc slow down patching and this might be a turn off to start.
you can do complex things with simple modules just by patching up complex things. some modules try to be all things to all people and they often fail. usually patching can get you there if you have a handful of modules to patch up. think in terms of functions.
if you want something you can compose entire songs on then find the right sequencer.
don’t buy like 5 expert sleepers distings. lol. some people do. one is good to have because it can do so much and saves so much space and $$ in a small system.
don’t overlook doepfer modules. there’s plenty of really essential great ones and they’re affordable. don’t worry about getting the latest/newest thing. sometimes the older version is the thing that has the magic sauce.
don’t overlook utilities… attenuators, mixers, vcas etc.
with 2 analog oscillators, a good wavefolder and a good filter you can make all kinds of great sounds.
oh and yeah… MATHS is really that great.
you don’t need a wall of modular to get things done. 2 or 3 rows of the right things and you can really explore a lot of territory.
VCV rack is a good learning tool. any modular environment is actually a good learning tool because of the concepts you acquire.