22 LR have a selection of boxes and bricks, standard and high velocity
22 mag (tough to find, if you stock it word will get around and it will sell)
22-250 45-55 grain varmint loads
243 80-100 grain deer loads
270 130-140 grain deer and elk/moose loads
7mm Rem Mag 140-160 grain deer and elk/moose loads
30-30 150 grain deer loads
308 150-165 grain deer and elk/moose loads
30-06 165-180 grain deer and elk/moose loads
300 Win Mag 180-200 grain deer and elk/moose loads
12 gauge a selection of steel and lead bird shot and a little bit of buck shot, couple boxes of slugs
410 lead bird shot and some slugs as well
That covers the most common cartridges and is just a guideline, just check out what other businesses are stocking and find out from coffee row what the locals want but can’t find, keep track of what customers ask for and you’ll find the trend for your local area.