As Debra says try various stuff and see what works for you. A delight for me was coming across a recipe for banana and peanut butter muffins. I have as little or as much as I fancy at a time. Peanut butter sandwiches will do but not too many. Malt loaf is another favourite but again, too much and it becomes off putting! A banana carrier is now an essential item of kit for me as they can become too mashed on long runs. I find that raisins make a welcome change. See whether you prefer sweet or savoury. Don't be put off trying, just think of it as a picnic on the move over several hours. Jim
Although Jenn Gaskell is a little older than you I know she started ultras at a relatively young age. Here's a link to some info about her. http://www.montane.co.uk/athletes/jenn-gaskell
I wonder if you're looking at the High Peak 40 which is in September. It's not easy having plenty of hills but would be a good choice for several reasons. You have a good amount of time to prepare for September so I'd say Go for it, like others here. As for tips, tell us what you'd like to know about eg food, kit, training. All the Best Kelsey.
Oooooh T Rex! I was wundrin about about the OMM pants as a late Christmas pressie to self (I have the jacket, not smock & very happy with it). I didn't try the Minimus.
From lurking elsewhere I'd like to say I'm glad to read you're getting back to running T Rex, after the clavicle. My young lad did his in October. He played football twice in December, was upended & now off for 6 weeks .