Shop the sales and rebates.
Might be as simple as buying a box here and there to build up the supply over time.
Also - for bulk shooting, nothing beats a good .22 rifle. you get trigger time and it's cheap. It isn't glamorous but with a good .22, you can shoot a .30 cal bullet hole as a target at 100 yards. $40 for 500 rounds.
You can shop around and see what ammo is available and how much $. Then decide if you want to get another rifle that shoots cheap ammo. 223/556? 7.62x39? Etc.
Reloading is a cost effective way to shoot more but it ultimately takes more time. The upfront cost is manageable if you are willing to use the basic equipment and not try to set yourself up as a professional reloader. Some ammo is sold at prices cheaper than you can reload, others can be reloaded for $1 or more savings per shot. If you are gonna shoot 1,000+ rounds per year you probably want to reload. If you are gonna shoot 100 rounds per year, just buy ammo by the case.
Fun question - have you figured out how much you want to have on hand? Don't answer this but think about it.