The truth is, what you're going to have to do is just take the plunge and get some experience. There are all sorts of variables that are highly individual but won't make sense until you have some modules in front of you. This individualization is one of the beauties and joys of modular, but also makes it difficult to give advice. Everyone has their favorite manufacturers and modules, but that doesn't mean you'll like the same ones.
Do you like one-knob-per-function modules or are you okay with menus and button combinations? Do you want lots of panel space to tweak knobs, or are you okay with having tiny knobs and jacks all bunched up together, making it hard to get your fingers in there? And so on...
My advice is always to do your research and go slowly, only buy modules that solve problems that you cannot solve with modules you already have, don't be afraid to sell off modules that don't work for you, invest in a bigger case than you think you need, and have fun. You probably will spend more than your current budget in the long run.