Hobbies And Interests
Steal
As you develop your abilities, Rikku's part of the grid will unlock Steal. While this may seem to be a weak addition at first, you will be able to steal rare items in the late game that are very difficult to find as drops. Steal is dependent on your luck attribute, which may be increased by use of the sphere grid or the Lucky skill. You can also use Jinx on your opponents to increase your relative luck. Stealing from treasure chests in the Omega Ruins can create Mimic Boxes, which are great for the gil that you will soon require.
Bribe
Rikku's last ability in the sphere grid is the Bribe ability. This power lets you pay off monsters so that they not only flee, but also leave a rare item behind. These rare items are essential to customizing your abilities for more powerful attacks and getting you out of potentially lethal fights. Bribery takes a lot of gil, so you will need to spend some time in high-yield areas such as the Airship quests and the Omega Ruins to build up your coins. You can also fight in the Monster Arena for items that sell for even more than traditional kills.
Customize
Now that you have a steady stream of rare items, it's time to put them to work for your party. Customization adds auto-effects to your party's weapons and armor, creating deadly combination effects that can kill enemies in a single blow. The most useful customization is Break Damage Limit. You will also want weapons that employ Deathtouch for its instant kill and Stonetouch for instant petrification.
Armors should be outfitted with Auto Protect, Auto Med or Auto Regen as these will keep your full party upright through most of the game's toughest battles. You might also use Auto Phoenix and HP + 30% for weak allies or combine the weapon customization Alchemy with an armor Auto Potion for constant and reliable healing.
The possibilities are near endless thanks to prodigious use of Steal and Bribe.