Definitely apply to more than one program. In my field, the acceptance rates for top PhD programs are 1-5%. The program I graduated from admitted 4 students this past year, out of a pool of about 200. It’s extremely competitive, so I recommend having reach programs and back-up programs. Especially without an MA in the field you want the PhD in, you’ll be at a bit of a disadvantage so I recommend giving yourself options. Since you are looking to start in Fall 2019, you have a lot of time left to do more research on compatible programs.