1. You don't build an FPGA rig like you would built a computer, you buy a ready made board and plug it to your PC through a USB cable.

2. Bitcoin is for using it like a currency/mining, if you want to learn how to program FPGA devices, then you should really be looking somewhere else, the software mining subforum is for "mining" discussions, not for "learning to program" so I doubt that someone there will teach you the basics of FPGA programming for Bitcoin.

3. FPGAs are already barely profitable, people who want to mine for a profit invest into ASICs, people who want to learn to program FPGAs learn something other than Bitcoin.

4. Besides the software, an FPGA device also needs a Bitsream to be programmed, otherwise it is useless.

5. A few days ago you posted that you don't want to invest into ASIC because you think you might not profit from it, now you are saying you want to buy an FPGA so you can learn to program.

6. What is it you actually want to do, mine Bitcoins or learn FPGA programming ?