Get your top wait type with sp_BlitzFirst @SinceStartup = 1
If your top wait type is | Then use @SortOrder = |
CXPACKET | CPU and Reads separately |
SOS_SCHEDULER_YIELD | CPU |
THREADPOOL | CPU |
LCK_** | Duration |
RESOURCE_SEMAPHORE | Memory grant |
PAGEIOLATCH_** | Reads |
WRITELOG | Writes |