There are many types available with manufacturers offering different advantages.
Entry level 4-channel transmitters can be picked up very cheaply though you may wish to purchase a six-channel set to give you some degree of future proofing.
Mid-range systems offer a larger number of channels in addition to computer systems that allow you to set up various profiles for the different models that you fly. They usually include a number of model memories as well as a timer so that you won't run out of fuel/battery.
At the top end there are some fabulously powerful machines on the market - with fabulously high price tags - though a number of the jet flyers will be making use of the extensive mixes and settings that these beasts offer.
One useful function available on nearly all transmitters nowadays is the "Fail-safe". This switches the engine to a very low throttle setting in the event of loss of radio link and is a very sensible precaution when flying any RC aircraft.
You will in time collect a host of tools and gadgets but the essential items at this time are:
Flight Box [£30.00 upwards] ~ to hold everything from fuel to spare parts and tools.
Glow Starter [£10.00 approx] ~ used to heat the glow plug during starting.
Fuel [5%] [£12.00 approx] ~ many types available on the market though synthetic is slightly easier to clean from the plane.
Manual Fuel Pump [£10.00] ~ to fill plane’s fuel tank
Start Stick or length of dowel ~ to crank the propeller
Model restraint ~ to stop plane from running off once engine is running [couple of sticks to hold the tail plane in place]
Nappy wipes and tissue ~ though not essential you will be glad you invested in these once you start flying as the plane will tend to collect fuel residue when flying.
Optional bits of kit to think about: 12v battery, electric fuel pump, electric starter, battery checker.
After thought [flight simulator]
Though not essential a flight simulator is a great bit of kit to practise on. There are many good quality ones available now for around £100.00.
It has to be said though that they not only offer a limited flying experience but also a great way of getting your head around the orientation of seeing your plane and moving your sticks. They also come with tutorials as standard.