you can do without the PR manager.
really, a level 2 (basic) is the most you'd need for now & is really cheap.
Now a doctor would probably be a good idea. Unless you don't care about frequent / extended injuries. (i'm talking about up to 1-2 real life month injuries). Maybe look at a level 3 (competent?) doctor or something.
just to be clear... a high level doctor doesn't mean you won't get injuries or anything... but it does make a big difference on how long injuries last & if injuries are single game only.