Honestly, 2 character slots is plenty to find out if you like the game. If you create a character you don't enjoy playing, delete it then you can create another one and try that. So you can, try all classes if you wish.
For example, create 2, play on number 2 , while number 1 is deleting. Create another, delete 2 while playing new 1 etc... Find out what you enjoy and what you don't enjoy. (It only takes 5 minutes for a character to delete.)
If you enjoy the game, sub then you get free HM coins (15 per day, need 400 for character unlock slot) or can earn them and use that to purchase more slots should you not wish to use real money.
If you aren't interested in doing this then it rather sounds like this game may not be your cup of tea.