Absolute essentails:
Fuel container, with a pump (pump can be squeeze bulb or hand-crank)
glow starter, rechargeable
"chicken stick" for flip-starting
Should Haves, if you plan to fly all day:
Transmitter case, to protect it and make transport easier (but not absolutely necessary)
Field box of some sort, either home-made or commercially available
quick charger, to recharge Tx and Rx batteries
Field battery, to power the quick charger
power panel, for use with the field battery, also allows you to recharge your glow starter
A few essential tools (glow plug wrench, prop wrench, set of allen wrenches, straight and phillips screwdriver, pliers
Extra rubber bands, for your wing
Extra prop or two
Nice to have, makes Life easier:
electric fuel pump (completely optional, the hand crank type is best, IMO)
electric starter, for days when the chicken stick just ain't enough

More spare parts (wheel collars, clevises, glow plugs,
A roll of clear packaging tape (makes great cover repairs for a tear)
As you progress in your flight training, you'll see what you use the most, and you can come with as much or as little as you want to bring