Complete Pangya Festa as Hana or Uncle Bob.
You unlock Caddies by defeating the Pangya Festa with certain characters. (Except for Pipin) You must purchase them from the shop first just like the players. Outfits for the Caddies will be unlocked and available for purchase when you unlock the Caddies as well.
All the clubs can be unlocked simply by focusing on completing the Pangya Festas for every character. You can achieve higher ranks by winning 'Pang' from playing rounds which will automatically add to your experience (assuming you won the match, in other case, just becoming PP) as well as become in game currency, and will build up until your next rank. (Rookie->Beginner->Junior->Senior->Amateur->Semi-Pro->Pro->National-Pro->World-Pro->Master)
Most of them being hard to come by, they are unlocked by completing certain tasks in-game.
To unlock a new character, beat Pangya Festa with another character. This means the first storyline of Pangya Festa, unless otherwise mentioned.