trackballs... they probably wont spin nice. I bought one for 20 bucks... and spent another 10 bucks on new rollers.... Still doesn't spin that great (good... not super smooth).
Consider buying a new one... There are 2 1/4 inch benson/imperials for super cheap around... if you go imperial, there is a ps/2 version....
But all in all... put this one off initially unless you have cash.
Joysticks - I have bought some great used joysticks, and some crappy ones. The crappy ones are fine for playing some games, but have no action....
10 bucks you have new one from
www.videoconnect.com. Get 2 and you wont be sorry.
Buttons... I go the other way... why? I bought 100 buttons (1/2 leaf 1/2 micro) and about 15 sucked... so I got 85 for 20 bucks or so. They are so simple that not much goes wrong with them (that you can't fix/cleanup yourself)
good luck