The basic guidelines are:
Each tempdb data file should be the same initial size
Autogrowth to tempdb files should be an explicit value in MB instead of a percentage. Choose a reasonable value based on the workload. Ex. 64MB, 128MB, 256MB, etc.
The number of tempdb files should be 1 per logical processor core up to 8. At that point the performance should be monitored and if more tempdb files are needed they should be added in sets of 4.
Ideally the tempdb files are sized up to the max they will need and never have to autogrow.
Use trace flags 1117 and 1118 for versions of SQL Server < 2016. In SQL Server 2016 these trace flags are defaults.
Trace flag 1117: when a file in the filegroup meets the autogrow threshold, all files in the filegroup grow together
Trace flag 1118: Removes most single page allocations on the server, reducing contention on the SGAM page. TLDR; no more mixed extents – use the whole page.
There are some good pieces of advice here, and Jeff includes a great example of a terrible setup.