Howdy! What are you using to trigger sounds? Are you hoping to just record one-shot samples into a DAW or do you want to treat your modular rack like a designated drum machine? The thing you can do with just what you have here is run the clock output from the noise/random module into the trigger in on one of the ADSRs. Run white noise out from the noise/random into one of the VCAs and the ADSR out to control the VCA. Keep the Attack, Decay, and Sustain near zero and play around with the release. Turn the clock speed up to how fast you'd want hi-hats to go and you've got that part of the kit going! For bonus, run the S&H out into the CVT input on the ADSR to get some varying length releases and humanize it a bit.
Without a trigger sequencer or at least a clock divider, there's not a whole lot more you could add to the kit as is. For a kick sound, tune one of the Brooks low and run it into a VCA. Have the ADSR go to both control the VCA and have it hit the pitch of Brooks to taste. Other option would be to put the other Brooks into another VCA and patch that VCA output into the FM in on the first Brooks, and use the ADSR out to control the 2nd VCA (and thus the depth of FM from one Brooks into the other).
Similar idea for a snare sound, except combine one Brooks and maybe the colored noise output in two channels of the Cloaks, controlled by the two ADSRs triggered at the same time, but playing with the release times to see what sounds come out of it.
As for modules I'd add, Pam's is great as a master clock and you can program it like a drum sequencer with a little work. A clone of Mutable Instruments Grids is perfect for a 3 piece drum machine, although no matter what you'll want at least one more envelope. For that, I think a clone of Mutable Instruments Stages is perfect for percussive things. Most percussion you really only need a Decay envelope, and Stages can quickly be 6 of those, but you can also set it up to be a mix of decay envelopes, clocks, clock dividers, S&H, or a bunch of other things (particularly with the Quiemem firmware).
Also highly recommend the Sound on Sound Synth Secrets series of articles for in-depth looks at creating a lot of different sounds from base synth components. Cheers friend!