Hi Lily the pony girl. As has been said before , it really depends on the horse or pony as to if they are going to get along or not.
All of my pastures are completely different in size ( some are yards, some are 1/4 acres and some are between 1-2 acres. Some I use in the winter, others I use in late summer as the sugar content in the grass is to high for miniatures during spring and leading into summer here. I also know what to use in replacement when my horses are lacking nutrients during the different seasons here.
Have you looked into local pony clubs or riding centres?. They may offer some classes for first time owners that will help you with the basic care of a horse.
Every horse and pony are different , so care will vary from one to the next !