Gatwick to Edinburgh via York - train questions

The walk-up fare from Gatwick to York is GBP 115.90. From York to Edinburgh is another GBP 90.50. You can save a lot of money on those fares by booking tickets in advance - but, if you'd rather not do that, you can also save money by getting a rail pass. The cheapest BritRail pass - valid for 3 consecutive days - looks to be US$181. If you'd rather not take your day trip to Edinburgh within two days of your arrival, a pass for any 3 days within one month is $230, which is still cheaper than the sum of the walk-up fares above.

Have a read of this about taking a train from Gatwick to York.

https://community.ricksteves.com/travel-forum/england/train-from-gatwick-to-york-direct-or-other-option

You don’t have to book ahead and you can be flexible – but it will cost a lot more than buying the cheaper Advance tickets to your destinations (that’s the downside of flying to an airport 300 miles away from where you want to be).

The risk in buying ahead is that if your flight is delayed and you miss your train, you may lose your investment or at least have a major hassle trying to exchange ostensibly nonrefundable tickets. Of course most flights are on time, or close to it -- but every once in a while there's a delay of many hours.