Unless you get a unit with motorised faders, i hate to say it, but the best controller for the mixer is a mouse/trackball/scroll wheel.
Watch any tutorial video, no matter what controllers they have on their desk they will 99% of the time adjust faders/pans etc. via mouse. Because it’s just so quick and logical with what you have on your screen, and you’re not forced to focus on a bank of 8 channels at once.
The biggest hangup with generic controllers and Cubase is how complicated it is to map to VST parameters (i.e. synth filter/envelopes/lfos etc.). That may or may not be a concern for you though.
But this is why i’ve got my NanoKontrol2 running via full Mackie Mode (i.e. it can control faders,pans,sends,vst) with an on-screen emulator as the Mackie screen. This is a really cheap (non-motorised) setup, and mimics an expensive MCU well. Took a bit of setting up though, as it’s a bit of a hack - but great for a laptop setup.
For cheap mixer control i’d probably be looking towards a single motorised fader such as the Faderport/many equivalents out there. You haven’t got to worry about which ‘bank’ of faders are in view as you only focus on a single fader at any time, and it’s always synced to the correct physical position. But these are around the 100 quid mark i think.
If you want drum pads, then i’d be more tempted to just go that route with the budget you have, and maybe not worry about the mixer control at this point (No matter how appealing it may seem).
And in regards to drum pads, it depends on the intended use, as to how suitable it would be for you. i.e. a 2x4, or 2x3 style pad layout isn’t going to match on-screen to Groove Agent very well. You ideally want 4x4 if that’s your intended use - and pads can differ greatly in quality too. If you’re trying to get a mixer and pad controller for 50-100 quid it’s gonna be pretty cheap quality.
That said, a nanopad and nanokontrol together is under 100 notes. Both very useable/functional controllers. - you just need 2x usb ports of course.