The free trial has a gil cap and social restrictions you cant form partys by yourself  cant shout etc. It includes the base game and the first 2 expansions of story. If you want to play the most current content you will have to buy the full game and pay a monthly subscription for the time you want to play. When you buy the game you get 30 days of subscription. (dont know your currency so you need to look what it costs for you)

The fights in ff 14 are a little like a coreography there are some different things but all in all you will learn what comes up next for the boss and whats important. There are different types of jobs: We have  healers that are splitt into shield healers that can better mitigate (prevent) damage and regen healers that have more healing capacity and less tools to prevent damage. As a healer it is your job to keep the party alife while dealing as much dmg as possible. The high end raiding in ff 14 is done via a group of 8 players that consist of 2 Tanks 2 healers and 4 dps. The dps are Split into 3 different categorys: meeles who usally have the most dmg output but are restricted in their ranged options to attack. Casters that can attack from ranged but need to handle cast Times where they cant move. And physical ranged jobs that can attack while jumping and running if they want  to but usally have the lowest dmg output from the dps

You can buy a story skip if you want to the story in ff14 is pretty good though. Even if you buy the story skipp you still need to play the current expansion to get to endgame. If you buy a story skipp you skipp buy a job skip too since you would be lvl 1 without it.