I have used many big containers of Nutricost brand from amazon , tasteless and mixes well. BulkSupplements brand has also been great.
To avoid any clumping with any of the mixes I add cool (not super cold) water 1/4 full… add all ingredients and then shake vigorously… then top up with water/ice after shaking.
I typically then add flavored electrolyte powders like Sports Research, Propel etc… then add Saltivate unflavored electrolytes (or similar) to get sodium where I would like it depending on weather/duration etc.