If you really want 100 IOs, the ZTEX board has it:
https://www.ztex.de/usb-fpga-2/usb-fpga-2.01.e.htmlThere is also a Debug motherboard with switches and LED:
https://www.ztex.de/usb-fpga-2/debug.e.htmlSmaller IO count but what seems to me to be the best 'starter' board is the Arty:
http://store.digilentinc.com/arty-artix-7-fpga-development-board-for-makers-and-hobbyists/The Arty has a fairly large FPGA so it is unlikely you will run out of LUTs. But it doesn't have much in the way of IO.
I only had a 32 channel logic analyzer so I used what is now an obsolete Spartan 3 Starter Board. It had 3 50-pin headers.
Another thing to consider with Vivado and Arty: You can implement an in-circuit logic analyzer. This is VERY powerful. You can probe just the components you want.
There's another way to skin the cat: Implement a long SPI register and use it to send both operands and receive the result. I was building an arithmetic unit like the PDP11-45 and I used a Blackfin board to grab the vectors and intended results from an NFS server. The Blackfin would grab a vector, send it to the FPGA, read back the results and complain to the serial port if it didn't like the answer. The reason for the horsepower of the Blackfin is that it had ucLinux and a full TCP/IP stack. I could see where a Raspberry Pi would be the way to go today as long as the SPI packet can be arbitrarily long (or segmented).
The NFS server was running on my Linux box and that's where I generated and stored the vectors. Kind of a long way around...
This SPI approach is a lot like JTAG without all the complications. It works very well once you get it set up. A few Python scripts (Raspberry PI) and you're good to go! I suspect it could be done just as well with an Arduino. Neither of these were available to me at the time I used the Blackfin. I would probably go for the Raspberry Pi since it has a file system, a console terminal, SPI capability, a C compiler or Python interpreter - yup! That's the way to go!