If you give a castle / town troops, it will increase the army and the tickets if its getting attacked. If you give gold, the castle/town will have more gold to buy equip for the siege. Not sure about gear but I heard the AI would auto-sell and not use it.
Here, in the FAQ:
Q: I sent some gear to an AI owned village but it didn't show up! Is this some sort of bug?
A: Every hour, neutral villages will recalculate the gear they will buy with the gold that they have. In the process, they sell all gear that they have on them for full price in order to buy new gear.
So, I think it does not matter what gear you transfer as it will be sold anyway, however the more expensive, the more gold the AI will have and better gear will be bought afterwards.
