You mentioned if it was best to shoot a few rds twice a month, or more rds once a month to improve your skills. In my opinion, going twice a month is more beneficial than once a month, simply because shooting is a diminishing skill that requires constant practice, this is where dry firing at home comes into play.
When you dry fire at home frequently several things occur. You improve your basic fundamentals of shooting, such as improving trigger control, picture sight alignment, (remember when you hit the bulls eye, can you replicate where exactly your sights were in relation to your point of impact. Were the sights perfectly aligned dead center a little high, a little low or left and right. All these are important to replicating your second bulls eye shot). Dry firing also improve muscle memory, endurance and strength.
I also believe that dry firing improves the functionality of the weapon you are using because it begins to polish the mechanical components that move with each squeeze of the trigger, thus providing a smoother working slide or trigger.
When I practice or dry fire at home if it is with a semi automatic pistol I place a sheet of paper arms length away from me with a circle the size of a quarter and a sharpen pencil inside the barrel. The point of the pencil towards the paper and the eraser towards the firing pin. I cock the pistol and squeeze. Try this 50 to 100 times and you will see the pencil marks all over that little circle if some of the pencil marks are out continue your practice until you mastered it. After that draw a smaller circle. If it is a revolver I like to use a laser and aim the laser like at an object squeeze the trigger in double action until I can get the laser dot to remain on the object every time I squeeze the trigger. This is difficult in double action.
Finally, at the range I always shoot 200 to 300 rds of 22 long rifle. I start at five yds because this way you can see immediately began to practice everything you have practice at home. First thing your picture sight alignment, than trigger control and than you see where the point of impact occurred. It does not matter where the bullet hits at first. Aim your handgun at the same place you did the first time and shoot, and repeat again until you have your bullet group. Than move back to the seven yd and 10 yds and 15 and so on and repeat the process. If all groups hit in the same area as the 5 yds shot your picture sight alignment is correct and your trigger control is in check. Of course impacts will be lower at further distance or higher depending on muzzle flip but if they strike in the general location as the first shot you are good. If it becomes necessary to adjust and you have adjustable sights than adjust accordingly, if fixed sight compensate by using Kentucky windage.