Aspiring to tech diving within caves or shipwrecks is an admirable goal and one that I share. While I enjoy looking at any marine life underwater, seeing things that very few people (let alone divers) will ever see adds to my antcipation.
Tom's advice is sound....take every training class that you qualify for, especially Advanced Open Water and Rescue Diver. AOW will build upon what you learned in OW and also expose you to some of the specialties that divers do, such as night, navigation, photography, dry suit, and others.
Rescue will teach you not only how to assist another diver in distress, but how to keep a rescue from happening through prevention.
Best advice is to keep diving every chance you get, and always practice the skills you learn. Just like the Aussie Cricketers and Footies, practice makes perfect.