It's not so much about the number of rounds fired as is it is how you fire them. Some shoot 200 hundred rounds and make no improvements or gain additional skills... where others can shoot 50 and actually improve their skills or gain new proficiencies. Here are a few tips to keep your sessions fresh while working on different skills to improve your fundamentals.
Vary your targets... try using dot targets where you fire 1 round per dot (1-2" dots). Start close and move the target back as the drill becomes easier and you are hitting each dot. This type of drill will get you moving from target to target and keep you from falling into the time/ammo wasting routine of dumping 20-50 rounds into a single target where you end up with a big ragged hole. While fun, there are many other things you can try.
Here is an example of a classic standard target...
A lot of ranges do not let you practice drawing from the holster... don't let this discourage you. You can always practice raising and firing from the low ready or retention ready position. This will improve your target acquisition skills and keep your range time more interesting. One round or double taps (if allowed) per presentation.
Firing using your strong hand or support hand (one hand shooting) is something many either forget to practice or they just don't think about it. Remember to use good form as you "punch out" the pistol, locking your wrist and slightly canting your firearm inward for added support (utilizes natural bone structure). Draw your other hand into the center of your chest for added balance & stability.
Try point shooting, where you don't acquire the sights and use your natural point of aim and your indexed finger to drive your POA (point of aim). Your finger should always be indexed or "high on the slide" anyway for safety... use this as your basis for your aim for point shooting. Most are amazed how far out they can accurately point shoot. Understand you should be trying for combat effective shot placement... we're not going for marksmanship groups here. Again, start closer and move the target her out as your skill & proficiency improve. This skill... more than others is important for surviving real world encounters where close proximity of a threat does not allow time for use of sights.
I'll post more drills a little later and add some pictures of targets below...
Shoot N' C or Glow Target type targets let you see your hits and are a nice change. I recommend the 6" target... I believe in the theory of aim small, miss small.
Another target that doubles as a rifle and a pistol target. One big target in the middle and 4 additional, more precise targets in the corners.
Taking a class from an experienced, reputable instructor at an outdoor range can be very beneficial to new AND experienced shooters. Our outdoor classes incorporate lots of holster work, movement, reload drills and malfunction drills as well as positional shooting. Our students go through 400-500 rounds on average per day. All learn drills and skills that they can take home and practice to keep their proficiency since shooting well is a perishable skill.