If it’s not required to be racked, I would consider the beat step pro. Affordable, two melodic sequencers (pitch, gate, and velocity) plus 8 drum triggers. Patterns up to 64 steps and a couple of different options for pattern chaining, muting, etc. Hard to beat for the price.

The chromatic modules are a good place to start, as you can get a VCO, VCA, Filter, Mixer, EG, and LFO all in just three modules for around $100 a piece. It’s what I did and don’t regret it. Definitely go for a 6U case. My rackbrute 3U filled up very fast and now I’m kind of stuck debating with myself if I want to get the 6U and have 9U which is more than I need, or switch to a different 6U case and sell my 3U or keep it as a separate case for a small system later. Either way it’s a problem I wish I didn’t have.