Gnome Ranger with Natural Illusionist.

How does the spell save DC work for it? Is it what the ranger's spell saving DC would be when I hit level 2? 8 + WIS mod + prof bonus? or is WIS replaced with INT for just that spell alone since INT is the spell-casting ability for it?

Natural Illusionist's Minor Illusion is based on INT, regardless of your class spellcasting ability.

Quote from filcat >>

Natural Illusionist's Minor Illusion is based on INT, regardless of your class spellcasting ability.

 So the spell save DC would be 8 + INT + Prof Bonus? Instead of the WIS that rangers go off of?

Yes.