That’s a tough one, a gecko that is both diurnal and terrestrial. 
I’ve heard some ‘micro’ geckos are mostly terrestrial, but I don’t know much about most micro gecko species. I’m not sure if Gonatodes are terrestrial. I know Sphaerodactylus argus are terrestrial and diurnal but I don’t know much else. You might have more options if you looked at non-gecko diurnal & terrestrial reptiles. I know some species of skink are quite small and often terrestrial. Did you have a size of enclosure in mind?