Hi swimman and welcome to the hobby !!!
Here is a short list of some things you might not have yet. Some of the items you may already have, This is just a basic list and you can add to it per your preferences.

Great Planes fuel station filling set ( mounts to your fuel jug and pump to transfer fuel to and from the plane.)

Glow plug igniter

Glow plug wrench

Chicken stick
(unless you are going to use an electric starter) DO NOT try to start the engine by hand flipping it. Use the stick and save some fingers !!!
(If you go with an electric starter you will need a field box battery and a glow panel to power it. You do not have to use these, the glow igniter and chicken stick will start the plane just fine.)

Field box to carry all of this stuff ( The one in the pic is a kit if you don't mind putting it together and painting it only costs about 20.00 bucks )

Expanded scale voltmeter to check your receiver battery with.

Stopwatch or timer to make sure you don't run out of fuel and have to try to glide in.

Small set of allen wrenches, screwdrivers and pliers.

Dale