First off, I personally use a variety of joysticks... I'll walk you though each one I've used.
Logitech Extreme 3D pro 20-30$: This was one of the first joysticks I used. it has the common 'sidewinder' action, which is that the joystick twists for torso twisting. it's a good stick, plenty of buttons, [which can be doubled up if you make one of the buttons a 'joystick shift' key but this is a feature on all sticks] and it feels good and fairly natural. still a tried and true stick you'll hear a LOT of mechjock's talk about, and with good reason, the stick is stable and good. I have both the standard and the 'force 3d pro' which is a force feedback version... both are good sticks.
Saitek Cyborg v.1:20-25$ The Cyborg V.1 is a decent stick, but it's definatley an entry level stick, it has a throttle built in[as will all sticks I review] and a few buttons to choose from but really, this stick felt... lacking. it's still quite a responsive stick, and if you don't want to pay any more than 20 bucks for a stick, this is a decent buy, still I'd spring a bit more money for one of the other options.
Saitek X45 flight control system. 20-50$
This is the older version to the x54 flight system that many people use. It's a sturdy hotas setup that offers quite a bit in the way of buttons and options. the problem I've run into with this stick is that in Mechwarrior 4: Mercs, the secondary hat switches do not regester as buttons, and thus will not read for the game. That said, this is still my primary HOTAS stick, and one that I still use constantly to this day. The primary issue i've had with this stick is that the buttons feel a bit... cheep. it's not a HUGE problem, but it does feel kinda meh. still it's my most highly recommended stick. The only issue you may find with it is that the joystick itself does not twist, instead on the throttle is a 'rudder control' rocker, which you would use for torso twist. I personally prefer the rudder control rocker to the twisting joystick method... but that's mostly due to how I set up firing groups on my additional firing studs on the joystick.... it's a personal prefernece.
Thrustmaster Top GUn Afterburner. 30-45$
This stick is a bit unique also it feels a bit loose, and that wasn't something I could fix while I owned this stick, It was however, my first HOTAS stick, and as such I feel in love with the options it presented me. It has plenty of buttons, and it's most unique feature is that you can switch between the rudder lever on the throttle, and twisting the joystick for torso twist... it offers both.
I personally felt this joystick was a bit, floaty, and didn't offer the response the other sticks did.
Last, but certernly not least....
The VTC [Vertical Tank Controller] Steel Battalion X-box controller. {Good luck getting it for less than 200$]
This, is in a way, the holy grail of Mechwarrior simulator controllers, offering 45 buttons [that's including toggle switches] the Steel Battalion VTC is a beast of a controller, also it take some work to get it honestly working the way you want it to, first off, you have to buy an x-box to USB dock to plug the controller into... well that's assuming you have the 200 bones to throw down on this bad boy. It's also assuming you have windows XP as the controller has issues working with anyhthing above that [no one's written a driver for it for modern OS] Now this controller is far from perfect for Mechwarrior, however if you want to feel like a true Mechwarrior [and be a bit closer to an accurate mech cockpit setup as described in the novels] this offers two joysticks, one which control torso movement, the other turning... the footpedals your forward and back movements, while the 'slide step' control from steel battalion functions to fire your jump jets. the gear shift takes you though different preset speeds...
really with this controller, you need the MW4 profile that was written, that way you have a diagram of what everything does. I've only played a couple of matches with this controller, what I will say is that the right stick feels very good, and while a bit slow, is accurate in it's movements, allowing you to aquire target's fairly sure... it's simply an akward controller to get used to. Still fun to play with.
My overall recommendation is to get the Saitek x45 or 54... it feels good, it's responsive, and it's not overly sensative.
Please note, this is almost a word for word post of my joystick review over at Mektek.net and as such, some things may not apply to Mechwarrior: Online.
Also, after thinking about it... The VTC may be the way to go for MWO, however for your price range, I have some decent choices here.
And to the hater's for the Logitech 3d Pro... NUTS! [just kidding] It's a decent stick... it excels nowhere, but for the pricerange... is solid.