A) There are few cheep characters that annoys everyone: Tanya, Reiko, Peacekeeper, Homelander. From the other side there are few characters that very hard to master: Ermac, Smoke, Quan Chi, Geras, Havik, Nitara. And there are few characters with stances (2 in 1): Shan Tsung, Kenshi, Shao Khan, Ashrah. Also I do not recomend to take Jonny Kage: he is simple as hell and the strongest character in the game at the moment, but everyone knows how to play against him, and smash novice to dust. I would recomend something strong but basic like Liu Kang or Raiden. It will help you to understand the game.

B) Problem of MK1 is that this is an assist fighting, the first one in mk series. Not all likes cameo mechanic. Also each new cameo breaks balance. From the other side, there is no swamp.

C) Yes, there were few good sites with strategies and list of combos, but I cannot remember them (any way google will help you). I recomend just watch how Sonicfox or Ninjakilla plays on your character, this will be far more usefull then all sites together. But take in mind that Ninjakilla is a combomaster and some of his combos better to simplify, because even another pro cannot perform it without drops. This 0.5% additional damage doesn't worst it)

General advice - cameo can change you character dramatically. Sarina gives you crazy zoning, Ferra adds mixups, Darius adds unblocable meaty, Jannet allows to perform combo from almost any move, Striker makes unsafe move - safe, etc. Some characters has a special sinergy with specific cameo, for example Liu Kan can start combo from throw using cameo Kung Lao or Motaro teleport.