223 is going to be by far the cheapest round to start with it's a good round for varmints at range, but you have options such as 25-06,6mm,6.5mm,260,22-250 etc etc. Without getting into ballistics, bullet weights, fast barrels, hand loads etc to much honestly the 243 it has the advantage over the 223 with wind, bullet weight an drop and it's also pretty common like the 223.
You can study all this an make a choice really a body couldn't go wrong with any of the above calibers and they're even more that I won't list, but some rounds do more an have the advantage over others it just depends on what the shooter is after vs cost. If you are gun shy meaning you do things just before you pull the trigger you should honestly fix that issue if you have it and always be aware of your surroundings! I personally prefer a 270 as my all around caliber especially with hand loads. If you are just out for killing varmints the majority would be hard pressed to beat the 223 it's a decent effective cheap round. Once you have chosen your cartridge focus on the make of gun and the glass this would be where I'd focus my time at the most if I was looking for a new long gun.
You can study all this an make a choice really a body couldn't go wrong with any of the above calibers and they're even more that I won't list, but some rounds do more an have the advantage over others it just depends on what the shooter is after vs cost. If you are gun shy meaning you do things just before you pull the trigger you should honestly fix that issue if you have it and always be aware of your surroundings! I personally prefer a 270 as my all around caliber especially with hand loads. If you are just out for killing varmints the majority would be hard pressed to beat the 223 it's a decent effective cheap round. Once you have chosen your cartridge focus on the make of gun and the glass this would be where I'd focus my time at the most if I was looking for a new long gun.