I am intrigued by this game and I am a long-time comic book fan. If I decide to take the plunge and give this game a try, should I just start with Civil War starter pack since it is the newest version? Or, is one of the older sets better? Advice on how to get started would be greatly appreciated. What I personally would recommend is a starting set and the corresponding 8 booster card + dice of the starter set heroes from an online store like coolstuffinc. In my details, each starter set contains 8 fixed heroes with three "variants" and two dice each. In my opinion two dice are not enough for the lower cost heroes. Hence buying the 8 booster card of the same heroes will give you the same eight heroes but this time with four "variants" and three dice each.
I would then recommend getting another starter set and doing the same thing for your opponent. You should then be able to do a simple draft with the sixteen heroes that you have, or play constructed. I have done this for the first four sets and so have enough "critical mass" already to play in any format I want ...