When going to the range, I find it convenient to to just grab ammo from my ammo that I already have at home. The trouble is, I have good intentions of purchasing more to replace the stuff that I used but a lot of times I forget and many times it doesn't get replenished until I notice my stock is lower than I like to keep or that it is hard to get and I'm kicking myself for not purchasing and saving more while it was around and affordable. It wasn't until this last ammo shortage that I have changed how I use my training ammunition. Instead of digging into what I keep at home, I pick up ammo from the store before my range trip. This way I am not digging into my back stock.
I try to only use as much ammunition at the range that I purchased at the store. When I used to just grab from what I had already, it would really surprise me at how fast my stash would disappear even with only grabbing small bits at a time. It is nice to have a back stock of ammunition to get you through the hard times of when ammunition is hard to get or when it is more expensive. Then you can still at least go out and practice a little bit during the hard times. Maybe you don't get to shoot as much as you would normally but at least you are still getting a little bit of practice even if your range trips are a little more spread out or only have enough to shoot a box or two of ammo at a time. It sure beats not being able to shoot at all until the ammo hits the store shelves again. Also, it would really be disappointing to not be able to attend a class that is coming to your area just because you didn't stock up a little bit of ammo.
Right now isn't a bad time to start stocking back up again, many calibers are dropping pretty close to what they were running a few years ago and it is a little easier to find even in case quantities lately. Even if you can't afford to buy whole cases at a time, buying a box or two every pay day can really add up... Again, as long as you are not shooting it up as fast as you are buying it. Hope this helps, I know changing my system has really helped me out and it is nice to not have to panic as much when ammo disappears because you have been preparing for it and squirreling away a little bit at a time.
Have a great and safe weekend!