Depends on the kind of shooting you are doing......
Generic response:
If you can, buy 500 of one particular lot and brand.
If you are like most other guys I know that reload for .270, you aren't going to the range every week and blasting off 20 or 50 or 100 rnds. You are going to build a load for particular rifle and then maybe shoot 20 shells per year to keep current but most of your 'plinking' will be with a rimfire or a SKS.......
So if you buy 500 primers, you are good for the next 10 or more years.
Now if you are planning on reloading for .223, .308, .270, 30-06... etc... This advice is ok to get you started, but pretty much usless otherwise.
Cheers!