I find that at different times, I prefer more or less tahini, more or less lemon. Never could figure out how to balance until I hit on the solution recently:

Leave out the lemon and tahini at first - blend everything else (including the cayenne, jalapeño or whatever else you like if you like it HOT).

Add 2 TB tahini, 1 TB lemon juice (or whatever works best for you)

Too much tahini? Add a bit more lemon juice.

Too much lemon juice? Add a bit more tahini.

(If you're not sure of the amount of garlic, add that bit by bit also)

And most of all, don't salt it until you take it out of the blender. It almost always tastes saltier after you leave it sitting for awhile, and if you put too much salt in at first, it's almost impossible to undo.