Where on my schedule C would I enter the following for a customer appreciation event held at a venue:
cost of renting venue
cost of catered food
cost of gifts
cost of supplies needed for event
cost of decorating( a company was hired)?
You could list each individual item's description and its cost in Part V Other Expenses, which when totaled will be transferred to Line 27a. See image example below.
Be advised that there are very strict rules pertaining to entertainment and gift costs of business
"If you give business gifts in the course of your trade or business, you can deduct all or part of the costs subject to the following limitations:
"You can no longer take a deduction for any expense related to activities generally considered entertainment, amusement, or recreation. You can continue to deduct 50% of the cost of business meals if you (or your employee) are present and the food or beverages aren't considered lavish or extravagant."
Be sure to keep receipts for all the various costs associated with this event.
IRS Pub. 463 - Travel, Gift, and Car Expenses (beginning on pg. 17 & 14, respectively)
TurboTax article: Are business meals considered entertainment?