You can get by for a considerable period of time with a container with fuel, fuel pump, 12V gelcel battery, glow plug igniter, starter or chicken stick, If you use chicken stick you won't need the gelcel. A field box can be a cardboard container, a sturdy one. If you get the gelcel and starter you should build a field box and put a power panel on it. You can see the field box design in lots of ads or look at what the other pilots at your field have. You should have a couple of spare props and a four way prop/plug wrench and at least one spare glow plug. If you can easily find one a spare prop nut may come in handy although it's probably not essential. You will, over time, accumulate a lot of things you can't live without and later decide you don't need all of it. Then you will start trying to eliminate stuff and eventually try for a smaller lightweightfield box with only essentials.
Have fun !