There is a great book about this called "Right It" by Alberto Savoia. One of the main points is that you need to get your own data and other people's data have very limited value. So, approaches like market research, hiring agencies, analysing competitors all sound like nice shortcuts to get the job done quickly but have a big risk of being misleading.
The "Right It" way is to define a hypothesis and go out and test it the easiest and cheapest way you can do. It sounds like more work but will give you additional insights from your target customers that will be most valuable to the idea you want to test and you can't find this information anywhere else because nobody else is trying exactly what you want to try.
Sending you a referral code on DM