@buddy-99
Many of the experienced shoppers are not going to share their "favorite" MSC with you as it is a significant part of their income stream and they have taken time to develop a good relationship with the MSC. Moreover, we all have different preferences and needs which leads us all to have very different opinions of which MSC's are the best. In other words, my favorite might be a real stinker to you.
I suggest that you sign up for as many companies as you can. Folks who have been doing this for a long time are with over 100. There is a HUGE list linked at the bottom of this page. All of my favorites are on that list. Start with the "15 Most Discussed Companies" as they are all larger companies that are likely to have work near you - even in rural Ohio.
I made a much longer post on the "New to Mystery Shopping - Questions" thread that might be useful to you. I answered an inquiry about how to maximize earnings.
Hard work builds character and homework is good for your soul.