In this particular case I would have NO autogrowth. Make your tempdb file(s) consume the ENTIRE 30GB on SQL Server startup. Now you get ZERO fragmentation and all 30GB of space is immediately available to any and all queries without any growth. Consider having Instant File Initialization enabled to speed the file creations at startup.

I may have missed it, but where is your tempdb log file at? That could have an effect on the above statement if it too is on the same drive (which is suboptimal but may not be avoidable in smaller environments).