New online shop for existing Wordpress site

We have an existing website built in Wordpress and want to add an online shop. There are 9 product categories, each with numerous products that need to be featured. These should be searchable by category, price, condition (products are second hand) etc. We also want tabs for New Arrivals and Hot Deals. So products may appear under more than one tab. i.e. it could be under a specific category and/or new arrivals and hot deals.

This is a South African company and we require integration with our country's payment gateway: Payfast. We do not want Paypal or Stripe integration as they are not used here. Delivery is by arrangement - or buyer can collect direct from the store.

Client has no technical knowledge, so image uploads need to be controlled in terms of size/dimensions to achieve a uniform appearance. They need an idiot proof backend dashboard to control stock, orders, deliveries etc., as well as auto responses to orders placed, payments made etc. Any other features you can suggest would be appreciated.