100 Round Practice
To improve your shooting your practice needs to be more than "shoot up these two boxes of ammo".
You need to plan a set of drills to work on specific skills. Here's a sample 100 round practice session.
1) Set up a 6" paper plate at 25 yards. Dry fire 10 times at that target from seated/benchrest position. When you dry fire, hold the trigger back after the gun goes "click". Hold the trigger back as you manually cycle the slide. Then slowly release the trigger until it clicks. That is as far as you need to release the trigger after each shot. Do not slap the trigger and then let your finger fly off the trigger. Ride the trigger back and forth and concentrate as hard on a controlled release as you concentrate on a controlled press.
NOTE: the trigger reset technique is specific to the semiauto handgun with a single action, single action 2nd shot, or safe-action trigger. It does not work well for double action revolvers nor for double-action-only semiautos. For those action types the shooter should let the trigger all the way out to full release for each shot and press it all the way through for each shot. It is still a good idea for the shooter's finger to remain in contact with the trigger during the press and release, but attempting to 'stage' a double action trigger typically does not produce good results.
WARNING: if you are shooting a handgun with a short reset length and light trigger pull (for example a 1911 style handgun in .45 ACP), it is essential that you maintain a firm grip on the pistol and hold the trigger back hard as the gun recoils. If you release your grip and/or the trigger and then attempt to 'get back on track' by pressing on the trigger, odds are high that the action has already reset and any pressure you put on the trigger after releasing it will cause the gun to fire, possibly with the muzzle elevated such that your round might not impact the backstop. The first time that you attempt the "trigger reset" skill during live fire should occur when your target is as close as possible to the backstop, and you are at 3 yards or whatever the closest safe distance to the backstop is - not 25 yards from the backstop as recommended in the next step. Other measures that you may want to take to minimize the risk of negligent discharge while learning this skill: practice this skill with an Airsoft gun or .22 caliber handgun before attempting with a larger caliber handgun; load your magazine with one live round followed by one dummy round, so that if you release-and-snatch on the trigger after the first round fires, that the hammer falls on a dummy round, not a live one.
Do not proceed to this next step until you have demonstrated that you can keep the trigger held back through the entire recoil cycle and only release it after the gun is back on target. It is every shooter's responsibility to know the limits of his/her ability to safely handle a firearm and stay within them.
2) Shoot three 5 round groups from seated / benchrest at 25 yards. Use a 6" paper plate as the target. Shoot the best groups you can. On every shot, hold the trigger back hard. Do not release it until the gun is back on target. Then slowly release the trigger until it resets, then press slowly. Measure your group size for each drill and write down those numbers.
3) From two handed standing, dry fire 10 times at a 6" paper plate at 25 yards. Use the same trigger control technique.
4) Shoot two more 5 round groups at 25 yards from two handed standing. Measure the group size and compare them to your benchrest groups. Ideally they should be the same.
5) Set up one 6" paper plate on a target at 7 yards. With an empty gun, aim at the target. Press the trigger until you reach the prep point (right before the shot is going to break) and release the trigger, keeping your finger in contact with the trigger all the way out. Do not let go of the trigger. Work on doing this smoothly in sets of 5. Aim in-out-in-out-in-out-in-out-in-out. Watch the sights the entire time. The goal is zero sight movement as you manipulate the trigger.
6) Load. With the gun aimed at the 6" plate, shoot 5 shots into that plate as smoothly and consistently as you can. The goal is to ride the trigger back out to the reset point, and no farther, as the gun recoils, so that you can start your press as soon as the sights are back on target. If you do this right it sounds like 5 equally spaced beats of a drum. 1-2-3-4-5. If it sounds spastic 12--3---4-5 then you are not consistent in your grip and trigger control. Goal is all 5 on the plate. If they aren't on the plate, slow down until you can do it properly. Repeat this drill 4 more times.
7) Repeat drill #6 with a 6" target at 3 yards. You should be able to go a little faster but the goal is consistent shot to shot times and precise trigger control. 5 runs of 5 shots.
8) Set up two 6" paper plates about 1 ft apart (left to right) at 5 yards. Start with a dry gun aimed at the left plate. Move your eyes to the right plate. Press the trigger as you move the gun to the right plate.
The gun should stop moving, sights on the center of the right plate just before the gun goes 'click'. Rack the slide, aim at the right plate and repeat the drill going right to left. Do it 10 times each direction dry.
9) Load. With 6, 8 or 10 rounds, start aimed at one plate, shoot it, move your eyes, press the trigger and move the gun, shoot the other plate, swing back to the 1st plate, etc. L-R-L-R-L-R-L-R
Ideally your shot to shot time from plate to plate should be the same as your shot to shot time for the 7 yard 6" plate. Run this drill in 6-10 shot segments to finish off what's left of your 100 rounds.
10) Dry fire 10 times at a 6" target at 25 yards. Watch your first dry shot carefully to see if the sights move. If you are developing a flinch you'll see it on that first dry shot after all that 3 yard blasting.
Those simple drills will teach you accuracy, trigger control, the relationship between speed and target size and sight picture, consistency in grip and trigger control from shot to shot, and the basics of target acquisition.
These don't require any special facilities or fancy targets and can be run w/o a holster or a shooting timer (although you can modify them to use them if you have them).
If you find yourself flinching and throwing shots low left (for a right handed shooter), buy some dummy rounds and stick them randomly in your magazines as you practice.
These drills are good for anyone at any level because you always shoot tighter groups or shoot "clean" on the plates faster.