There is quite a choice in the 50 $ range . Say at least what kind you like - is it a traditional looking , military style , should it have modern sh*ts like one hand opening linear/frame lock , how will you carry it - in the pocket , pouch , with clip or without ....
I don't want to be offtopic so besides the famous tenacious/rat my advise is :
1/ buck 110/112 :
+ solid , nice looking , realy well made , good heat threatment of the blade , strong back lock
- big and heavier than modern knivese , no pocket clip
2/ queen cutlery country cousin :
+ nice durable tool steel , pocketable size , don't look dangerous to non-knife persons
- d2 can get rust if you are not carefull , can be dificult to sharpen if you are unexpirienced
3/ SAK farmer
+ thick aluminium handles , good number of tools on it , nothing on the back side which makes it more pleasant to use , good enough steel for pocket knife that is quite easy to sharpen
- can't find one , maybe the lack of any locking mechanism but it doesn't bother me .