How to avoid mold in shower caulk?
Isherwood's right &amp; make sure you're actually getting the blowing air from the bath fan on the outside of the house. Also, after showers or baths get into the practice of letting the fan run for another 15 or 30-minutes.

You just want to fill, actually fill, that crack below the tile is all. Squirt caulk INTO the gap &amp; then force more caulk into the crack with your finger or a putty knife &amp; repeat until it's full. Your closed palm should be facing the wall &amp; not down toward the tub.

There's no need nor benefit in trying to make a ramp for the water. Water sitting on the caulk rather than beside it is mold's friend. Your caulk should look largely like your grout lines, it should be thin, tight &amp; flush with the tile face.