Hi. How does one go about buying an FPGA.. i have a desired LUT Count.. let's say 200,000.. what's more I should focus on ? I have been asked to get one which can be atleast 6 times the capacity based on our current IP utilisation.. New to this ! Any help or advice would be great. Thank you.

Don't confuse LUTs with standard cells. Depending on the architecture and utilization, an FPGA LUT can be the equivalent of 10 or more standard cells. And as Arman mentioned, most large FPGAs have dedicated resources for RAM and other common components, so if your design uses many standard cells to implement, say, a register file, then it can most likely be implemented in a dedicated FPGA macro and not use up any LUT resources.

Mine is an Ethernet MAC IP, and the IP team lead wants to port bigger IPs in future. So, for making a future proof buying decision.. this was suggested to me.

You can check https://corescore.store to get an indication of the relative size between different FPGAs