I have played this game over 350 hours, and I have only put $1 into this game, which was when I first started playing. Personaly, I do not recommend that anyone put money into this game because a lot of people have already done that, so the outcome would be rather disapointing, but that is left to your discretion.
This game has very interesting machanics for a puzzle game and the fact that it is Marvel is very cool. I also enjoy the animations for the character abilities. Additionally, the story content is usually humorous and fun to follow.
The game has changed in a few ways over the last year.
First, when I started playing this game it was almost imposible to win in PvP or random events because people that put lots of money into the game had better characters at much higher levels. However, I continued to play and found ways to deal with it. But there is better news for new players. The game has been switched so that players are paired with other players around thier average level. So basically add all your character levels and divide by two. This machanic also tries to push people away from the idea of getting one high level character because it would offset your team average and put you at a disadvantage in a higher tier.
Originally, there were certain lower level characters with overpowered abilities, which have since been nerfed or changed to even out lower tiers because earning certain characters is a chance of luck and not everyone is lucky enough to get those characters early on.
I think the game has overall changed for the better, eventhough there were a few changes I didn't like.
As a new player it would be much advised to play through most of the STORY content in order to build a decent team and obtain COIN to purchase more character slots (I would advise that you use COIN ONLY to purchase character slots because you dont get a lot and it costs more and more for ever 3rd or 4th slot obtained).
I hope this was insightful. If so please rate it as helpful.
Thanks and enjoy!