I was wondering which items and feats would help my druid (level 15) increase his tripping ability. I plan on doing a reach trip build in wild shape and tree shape form.
For tripping, we have several good options:
Fury's Call will allow you to add your Dex bonus to your CMB;
Tanden Trip is also an interesting option if you plan on tripping with an ally;
Wolf Trip will allow you to pick where the target will fall prone;
Drag Down will grant a free trip attempt when you are tripped.
Tripping Strike will allow you to make a trip attempt whenever you score a critical hit.
Riptide Attack might be interesting if you desire to drag enemies aswell.
The Gauntlets of Skilled Maneuvers will grant +2 on the chosen combat maneuver, a Brown Thorny Ioun Stone will grant +2 competence bonus on trips. Other than that, most trip enhancing magic items are magic weapons or weapon ehnacements.
However, a Wild Adhesive Armor will grant a +2 enhancement bonus on trip checks when using natural attacks. The Wild enchantment is required or otherwise your armor bonuses will cease to function while polymorphed.