Look at the matter with psychological prospective, which one you hate to do?, which one you like to do even without paying? (passion), then chose the one you like the most, be great at it (it is easy to master something you like ), then offer it to your clients and never deliver the core without paying.

At the beginning you need to understand your clients, then,
increase their gain, reduce their pain. this is the definition of value and this is how you can make money.

I assumed you already covered all other aspects like the value you provide to market place,your targeted clients, your channels to reach them ..etc, then I believe the best way for launching your firm is by telling a story which should explain WHY you do what you do, which also differentiate your firm.

There are plenty of research sources, some of them specialized in a certain area. but usually, the free sources are more generalize and poorer than the chargeable sources,
below some of the greatest well-known search sources:
1/ www.ourworldindata.org
2/ www.reportlinker.com
3/ www.statista.com