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start with a bigger case with a better power supply - you'll need it soon enough

start with as few modules as you think you can and learn those inside and out before adding more (and then repeat and repeat and repeat)

the tiptop tg one was afaik limited edition and so probably very difficult to source

if you want some tg goodness see the gristleizer modules from future sound systems

turing machines are often used for pitch - but require quantization

modulation - you'll want more - ochd is a decent start but something that's more controllable - ie triggered from a clock might be a good idea (Pams perhaps as it includes the clock) - as well as envelopes to turn the gate from the sq1 into something more than on/off signals - maybe an adsr module or Maths or Zadar or something similar

I'd also add more utilities - a wide ranging subject - sequential switches, logic, mixers of various sorts, attenuators etc etc - these are what add variety to patching and make patches interesting

see my signature for a philosophy of how to get the most variety from your modular for the least money - utilities tend to be, relatively, inexpensive

hope this helps and have fun