Or, use SKSE's instructions from their whatsnew: [Memory]
DefaultHeapInitialAllocMB= <default heap initial allocation size in megabytes, vanilla size is 512>
ScrapHeapSizeMB= <scrap heap size in megabytes, vanilla size is 256>. Then check \My Games\Skyrim\SKSE\skse_steam_loader.log to see if you have configured the pool sizes correctly.
Mods to Consider
Performance
Rejected/Not Needed
Test Procedure