I recommend doing your homework, then acquiring only the new/used equipment you NEED. If you get a kit, you'll get some of it but also stuff you either won't use or want to replace immediately due to quality issues. Buy good stuff ONCE versus replacing crap.

Offhand, you want your dies, a press, trimmer, scale, caliper, primer pocket cleaner, primer seating tool, ogive OAL attachment for caliper, shoulder measuring attachment for caliber if you shoot a semi-auto, deburr/chamfer tool, brass case brush, and some sort of powder trickler.

As for cost effective, even shooting a common 300WM I am floored at ammo prices. If I had to buy factory ammo I could not get myself to ever shoot the thing. Both pistol and shotgun you can get cheap ammo that makes it break even with reloading (but you get better quality reloading); rifle there is no comparison, the cheap .223 and .308 disappeared with the war.