I always use the smallest standard parameters (if not necessary to use advanced technology). Standards mean the PCB manufacturer offer it without extra cost.
For example:
I order my PCBs from Eurocircuits and they offer Class 6 PCB without extra cost:
Eurocircuits classification tableSo I normally use this parameters:
Minimum track width: 0.15mm
Minimum clearance: 0.15mm
Minimum PTH via size: hole-0.25mm, diameter-0.6mm
Minimum NPTH drill: 0.35mm
In your case we need mor information about your design. Mainly the package of FPGA.