Saitek makes several reasonably priced starter sticks from the ST-290, Aviator, Cyborg, EVO.
All of which would work just fine. Price is going to start at around 20$ for the ST-290 and go up from there.
The minimum you need 3 axis control, Pitch, Roll, Yaw (rudder), plus Throttle, 8 way hat switch for views, and a few buttons.
This is bare minimum, so don't settle for less.
Or you can do some searching on ebay and come up with a bargain on old MS Sidewinder Joysticks.
Not being made anymore, but if you keep your eyes open you can probably find good ones that are USB for about 30$.
(Read carefully, there are sidewinders sold on ebay that have no rudder, or hat)
The best of the best is CH gear, but you pay for it.
If you can afford it, by all means go for it.