Oh, you in deep here, boy! Its all over but the buyin'........
Figure which you want for a plaything, open sights or peep rear, or just a scope. Those with open sights are drilled/taped for a scope too if you want one later. Those without sights are more trouble to put sights on.
The sighting option will define your caliber choices better; from there pick a caliber that you fancy. As neat as the 30-30 is a downloaded .308 or 30-06 will be the same and offer more on the other end.
A .45Colt carbine is a hoot, but you can download a 45-70 to do the same and big, long cases seem just the thing in single shots. Same with the .444 vs the 44Mag. Should you ever find a .357 buy it, do not pass go.......
You should have a copy of their current catalog to drool over; you also have stock styles and materials with certain caliber limitations, though stocks swap on the rifles with no trouble.
All that said, I prefer (for a fun gun, easy to reload) a straight wall pistol cartridge that you can use carbide dies on ( and here I include the .444)
If you reload you already know why......if you dont, but might, just trust me on this.