It depends on what ship / equipment you have, how long do you think you'll want to stay out there, etc. For example, distances between stars become greater as you get closer to the edge of the galaxy, and in between galactic arms, so you want a ship with a long jump range for that.
Another factor to consider, since this is your first trip out, that you may get bored after a while and decide you want to do some fighting, smuggling or some other activity you need to be in inhabited systems for. It wouldn't do to get bored and then have 25k ly to travel back home

So, until you've had a taste I suggest not going crazy with distances, just do a few hours expedition for starters and see how you like it.