If you haven’t already, you are going to want to complete the quest, Stable Foods, provided by the Stablehand in Timberwell Village. As a reward for completing this quest, he will provide you with your first companion, 'Horsy'. 'Horsy' will follow you around and can run items to your bank for you and then come back to you on a short cooldown. 'Horsy' has an inventory size of 25 and for this reason, I consider this standard inventory size later on when we get into skilling money makers and money breakdowns.

You can transfer items to 'Horsy' by right clicking on an item in your inventory and selecting “Give to 'Horsy'” or dragging and dropping items into his inventory. You can send 'Horsy' to the bank or open his inventory through the dialog tree when speaking with him.

I would highly suggest one of the first items you get from Arty's Special Items Section Arty’s Library of Great Achievements’ Special Items Section would be the Horsy Whistle as for the low investment of 20 Old Artifacts, 'Horsy' will return to you 20% quicker which is quite an improvement when farming. Arty also sells Skillbook: Summon Horsy but this should be a low priority as if you accidentally dismiss 'Horsy' you can always pick him up at one of the various stables around the world.

Feeding Horsy up to 10 Carrot will permanently increase her banking speed from 144 seconds to 64 seconds.

— Sylynn