I bought a numpad so I could sample ergo clears. Now, I'm thinking about getting a second so I can sample berserkfan's jailhouse blues. For me, I think having the whole pad use 1 type of switch would give me a better idea of whether having a whole keyboard use that switch would be suitable for me. If you just want to compare a variety of switches to each other, I would recommend starting the list with the more uncommon switches like grays and modified switches like the ones I previously mentioned and panda clears, etc. Whatever spaces you have left over, dedicate to the more common switches. Maybe try to fit some gate Ron or kailh on there if it's possible. Or if you can't think of enough switches to fill the pad, consider using 2 copies of each switch.