Hey @BatmanFanGirl... I've played the retail system fairly extensively so I'll try to help.
I have found that hiring an employee can be helpful at first, but once you obtain certain rewards, it becomes unnecessary. One valuable reward to purchase is the faster checkouts reward. This is one of the first ones I work on getting. Since checkouts can take a really long time to complete, until you get that reward, an employee, or second household member, can be necessary in order to make sure everyone gets checked out before they get upset and leave. Once you have those reward traits, I find that one sim can keep up on all the checkouts on their own without difficulty. At that point, I find the employee is no longer helpful or needed.
Some other valuable rewards include the one for cheaper restocking. It immediately increases your profit of margin significantly, so if you're trying to make as much money as possible as quickly as possible, it is an absolute must. Related to restocking, the faster restocking reward is really important as it eventually makes restocking an instant interaction... Again, this one makes the employee unnecessary and allows one sim to successfully operate the store on their own. Until you have this one, an employee or second household member may be needed.
After getting all the restocking and checkout perks, I usually move on to the serious shopper perks, as they will increase your sales, but it is better to have the above perks first as they make it more manageable to handle the increased sales.
Sure sale seems like a great idea, but it has a cooling off period, so you have to wait a long time before you can use it again. I find that in a typical work day I can only use it about 3 times, so I would wait on that one until some other key perks have already been achieved.
Perhaps the most underrated perk that I didn't fully utilize at first was the superfluous surplus, as it decreases restocking costs by another 25%. It only lasts 12 hours but can be repurchased again and again. Now that I have most of the main perks purchased, I'll wait and not restock anything through the work day, and then at the end of the day purchase this perk before restocking everything. It really helps increase your profit margin and only costs 300 perk points, so usually, you can earn that many points within a work day before purchasing it to do the restocking.
One thing to keep in mind with your retail store is that sims typically gravitate towards the cheaper priced items. I had an electronics store and sims always veered towards the less expensive tvs, video game consoles, and cameras. They never bought the expensive computers, and televisions. That was until I stopped restocking the cheaper items. Sims continued to buy items as often as before, but now they only had the more expensive options, so they bought those items instead. So, if you want big profits, only include the most expensive options in your store. (Keep in mind I had the serious shopper perk at this point, so not sure how well this strategy will work without it).
As for the different categories of loiterer, socializer, and customer, I really don't notice a lot of difference. Loiterers might take a bit longer to purchase an item without a significant number of sales interactions, but they usually do anyways. I will often use the sure sale interaction on them so that they immediately buy something and leave, and then I can focus my sales interactions on sims that are already inclined to purchase.
