In addition to the items missleman pointed out, you’ll probably want to pick up a couple of extra props and a spare glow plug or two; plus a gallon of fuel.

The plane comes with a 10x6 wood prop. New pilots tend to have the prop blades hit the ground, and wood props break when that happens.

A somewhat flexible prop can handle the abuse a little better. A couple of possibilities:
Master Airscrew 11x5 G/F Nylon Propeller (OS recommends the 11x5 size for the engine)
Master Airscrew 10x6 G/F Nylon Propeller

The engine comes with an A3 glow plug. Your spares can be the same thing. OS also recommends the #8 for the 40LA.

Almost everyone has very strong opinions about fuel, props, glow plugs. Some are almost rabid in their love, or hate, of certain products.