@James Free i agree with what others have said about liability coverage. its not that expensive to get 500k or more on your properties. Your biggest risk is getting sued.
in regards to the appropriate dwelling coverage amount, its partially up to you. If you dont trust your insurance agent, find one you can trust. They can be a valuable partner in your REI business. I try to meet with my investor clients once a year or at least every other year to make sure the coverages are still correct on their properties. I go through all the details of the property with my clients, and my system will give me replacement cost amount based on the details i input regarding the building. I personally would want full replacement cost coverage for the full value of the property, so if there is a total loss i would be able to rebuild. Some investors i work with, only want enough coverage to protect the money they have invested.
For example, a house has a replacement cost of $150k, but you only purchased and rehabbed it for a total of 80k cash. Some investors would only want 80k dwelling coverage so that their cash investment is protected, others would want the full 150k so they could fully rebuild in the event of a loss. With State Farm, if you choose to lower the coverage to less than 80% of the determined replacement cost, your policy will switch over to ACV (actual cash value - aka depreciated value)
in summary, just go find an insurance agent you can trust and make sure you give them very detailed info about the property so that you have an accurate replacement value. then you can make your decision on how much coverage you want from there.