Hi, and welcome to the forum!
I started with the exact same setup, and I still have the line it came with on. It's an ok line; not horrible but not great.
I would recommend waiting a bit before upgrading to another line. If your just learning to cast and your like me, you'll snag more than your share of trees, rocks and telephone lines (don't ask.
Once you can cast pretty decent, then I would look to upgrade. If at that time you still want to stay in the cheap, I would suggest picking up a Cabela's brand WF line. I think they're around $30 so it's not a steep investment and their line is a step up from the Martin.
Oh, and also good luck on keeping this a "weekend hobby." It's more of an "every day of the week" hobby for me!