I would recommend to choose one FW from each year based on release date and perform staged update. If BIOS is also very old FW then update iDRAC and BIOS one after another in staged manner. 
Hi, Tomorow, I should receive the replacement motherboard for my R720. I expect a long run to update all firmwares. But I would like to know the best practice to update all firmwares. Is it better to updates drivers at the latest version immediately or we must follow an update path ? Is it better to update BIOS first ? or iDRAC ? or it does not matters ? Is it better to update each firmware manually or to boot with the ISO update tools (Platform Specific Bootable ISO) ? I'm concerned about this update methodology and I don't want to brick my board with this process. Thanks for all your advices
Firmware update - Best Practices