3 Sets are enough in general, you can do 4 if you want. I usualy stick with 3.
Well the rep number sure is important i guess, depends on what you wanna do. If you wanna get more endurance, you should do more reps. If you want to build muscle, you should do less reps but with more weight/more resistence. Like between 8-12 reps - but those reps should be every difficult, so you can barely make them - hence why you will have to ad more weight with time, to keep the reps low. If you can do those reps, but you stil have the strength left to push out more, you should increase the weight/resistence.