Straight Forward in a Crooked World put up a in-depth post about the calibers he reloads and why. Every reloader make decisions. How many calibers, how many different loads, how many presses, powders, projectiles,...? His choices are thought out and worth the time to read about.
I have avoided buying rifles in calibers I don't already have. I started with a 1903A3 and now have four rifles in 30.06, but don't own any other .30 caliber rifles such as .308 or .300 WinMag. I have kept my caliber choices to a minimum to avoid the added complexity it creates on the reloading bench.
It will creep up on you. You start with one single stage press, 3 or 4 die sets and a couple of cans of powder. Turn around and it looks like this (no, this isn't mine, I just like it).