squats, bench press, shoulder press, dead lifts. Lift with extreme explosiveness 1 to 5 reps no more. That technique is aimed at strength, and not muscle size. 8 to 12 reps is ideal for muscle hypertrophy which you definitely don't want, unless you want to be a bodybuilder. Also maybe you could bang out 600 pushups or so every couple of days with 200 or so pullups as well. I think everybody's body responds a little different though. I really don't think you need any weights at all to be a successful boxer however, but if implemented right it could definitely help. So many variables.
Look up some beginner weight routines, like Mark Rippetoe's Starting Strength or Bill Starr's 5x5. They are some good, basic beginner routines that aren't overly energy or time consuming, so they shouldn't get in the way of your boxing and conditioning.
I think the deadlift is the best for gaining strength! Pulls ups as well. I dont know about bench press though. how will that affect boxing? one thing is certain, look at any boxer. one thing they all have in common is a strong back! all!
