This trophy can be long to obtain, but if you keep your resources, that should be more fast.
You need : _ 1 minecart -> 5 iron ingots
_ 500 rails -> 192 iron ingots and 32 sticks (512 rails in real, but you must craft the rails 16 by 16, so 32X16->512).
The best way to make it, it's to make as in the first video, because you will not need a powered rail and so you'll save your golden ingots (for an armor or weapon).
But that's really long.
If you want to make it in a straight line without slope, you'll have to use powered rail (or a powered minecart, but after 2 hours to try to make it leave, I have stop this solution) , all the 50 blocks should be enough.Watch the second video.
You'll need : _ 1 minecart -> 5 iron ingots
_ 500 rails -> 192 iron ingots and 32 sticks
_ ~ 12 powered rails -> 12 gold ingots and 12 sticks.
_ 12 redstone torch -> 12 redstone dust and 12 sticks.
_ 1 lever
(Credit for videos to : Imjocavs and ZyGouNeTteLive)