Retail store?

well, talk to your customers alot using the retail interactions (this will also give you retail points which you can spend on helpful traits), dont do too high of a price markup at the start, customers are more likely to buy the cheaper stuff.
In my expirience I only had to grind at the start after a while I didnt really need to talk to the customers for them to buy something.

I have found that customers buy whatever, regardless of price. You could try to have similar priced items on the lot, even if they will go for the cheaper stuff first, if the price difference is small between the cheapest and the most expensive stuff, then you can ensure to have some sales. Make sure you have enough space between isles for the customers to browse and that they can actually reach stuff. There's a display case that customers can't actually shop from. I have found that some customers like to congregate and talk in the shop instead of buying, so I just send them home. Customers who talk, or who play violin or exercise are not customers, I always send them home. And, yes, some customers take forever to make up their minds about buying anything. Get an employee to manage restocking primarily and you manage the talking to customers and ringing customers. Your employee can do cleaning as secondary activity or you can do it after closing hours. I have a flower shop on the gallery that runs beautifully in my game and it's always in need of restocking at the end of the day and they even buy the big expensive plants. Also, the shop decor helps, it needs to be inspired or content, I forgot what it was but I put a mood lamp for it in my flower shop.

Carl has an excellent guide on retail.

https://www.carls-sims-4-guide.com/expansionpacks/gettowork/retail/