Like many have stated, what shops you do really does depend upon the reason you are shopping and what will help you with your regular day to day life. To just make money you can do phone shops, bank shops, electronics, audits, etc. If you like to get your nails done or have a wax job, those are usually reimbursement only - but that saves you money. Grocery shops pay a certain amount of money for reimbursement...you can do as many as you can (you can always put food in the freezer and non perishables in the pantry or storage closet). Gas shops/audits gets you free gas and a couple of dollars for purchasing something (a bottle of water or even a low dollar gift card - which can be used on the next gas shop with the same brand). Clothing shops with reimbursement and small amount of pay. It truly is all about what works for you!
Shops that do not work for me: there are now a handful of MSC's that are requiring shoppers to shop in two different departments at the same store and make a "small purchase" and the pay is very small when considering you are actually doing two shops - but they post it on the job board as one shop. I pass on these as they are lowering the pay and requiring more info in the reports. By the time you factor in time, gas, doing two shops and the equivalent of two reports plus a purchase; one is basically shopping at a loss. I have a couple of MSC's that will call regularly asking me to do a shop that's only "20 miles" away and is bonused; yet when I go to their job board and put in my actual address and the shop address it is more like 50 miles (because they use zip codes) and the bonus is $1.00! HaHa. No thank you. So beware of these phone calls/emails and always ask the specific address of the shop. There is one MSC that does primarily banks in my area and this bank shop is to ask for information regarding their checking or savings accounts, which they make it sound quick and easy, it is not - it ends up being at least one hour with the banker because they are asking about who all your accounts are with (banking, credit cards, loans, mortgage, investments, 401K, IRA, etc) and they ask APR, dollar amount balances and monthly payments, etc. and then they added that now we (the shopper) have to give our cell to the banker so they can download their app and show us how to use it. And it is required that you sit through all this because it is on the report if the banker when through each of these and what they said. Won't do that, because the banker will see all my mystery shopping apps and quite honestly, I do not hand my phone over to just anyone. There is one MSC I would do more shops for because the shops are easy and so is the report - the scheduler is the problem, in that they have a different full time job, scheduling shops is a "whenever they can fit it into their life type of job" and they are very slow to respond as to if they assign the shop to you or not (usually during the night when the shop is due the next day) - I like to plan ahead and not wake up to an assignment that I requested many days ago and did not think to go in to remove my request (that only happened one time to me - but have heard it happens regularly to other shoppers). I have learned through my adventures that there are schedulers who are not honest about the requirements of the shop or they only offer a small amount of information when they send out the mass email; and it is not until it is assigned to you that you find out that this very simple, quick shop with a very easy and quick report is really something very different. And last but not least are the MSC's that are not consistent with when they pay - and they do not comply with their own agreement. There is one company (that recently bought another company out) that can run well into the 4th month after you have done the shop before you get paid and most of their shops require you to put out money to do the shops. I do not mind paying money for shopping like restaurants, valet parking and retail shopping - but I will only do these shops for companies who consistently pay on time and within a 2-4 weeks of the shop. Keep in mind that some shops require that the shop be submitted through their app as soon as you walk out of the shop (there are some areas where you may not get signal, wifi, etc) and other companies that require that the shop must be completed and submitted within 6 hours of leaving the shop (which can leave you with having a short shopping day or you could make sure that it is your last shop of the day during business hours).
I realize the above paragraph sounds very negative - but I am offering information that you might encounter when or if you start doing more shopping and adding more MSC's. And I don't mean to bash any MSC, I have learned to navigate my way with many of them and know who to avoid - that works for me and my life. I would offer the advice that if you haven't done a particular type of shop for a company, then only schedule one close to you or where you are doing other shops to see what the shop really entails and what the reporting requirements and time will be before you request many of them...same for when starting for a new company. You may want to do a search of each MSC you shop for on this forum to get up to date information, as some have changed their business model, shop requirements/guidelines and payment schedules since you last shopped for them.
So, in summary, make the best decision for yourself and your life as to what shops will work for you either by being a full paying job/audit or being reimbursed for gas, groceries, clothing/retail, restaurants, fast food, etc. or a combination of pay and reimbursement.
Much good luck to you in your shopping adventures.
Please use the job posting area of the forum for referrals to your company.