I have watched folks try to 'get by' with bargain-priced firearms. From my observations, when you buy a really inexpensive firearm - you won't have a great experience and will likely buy another more expensive firearm. The result is simple - you could have bought a decent example for the money you've wasted. I'd suggest you, once you decide on your real purpose and the caliber you want, do without a few regular 'extras' in your life, save the moola, and buy a decent example. From my observations - and experience - you'll be a lot happier.
Now - caliber choice. Sure, .500/.460/.454 are impressive. Try to find the ammo on a Sunday afternoon. I was in my local WallyWorld yesterday - that ammo case has cobwebs in it, but there was .44 Magnum ammo. In fairness, pre-election even, they never carried .45 Colt/.454/.460/.500 ammo. I did see Winnie .45 Colt Silvertips at Academy Sports - and .44 Specials and Magnums. They both carried .45 ACPs - in stock at Academy - UMC 250/$95; OOS at Wally World at 250/$82. That's still a 'big-bore', even if it isn't a nuclear-level load.
In the long run - after a thousand rounds or so - the price paid for the firearm won't matter. Case in point - suppose the gun-fairy appeared and 'gave' you a .454/.460/.500 revolver - free! At $1+/round for 'just' .45 Colt cowboy loads, which would fit the .454 & .460, you could have bought 1k of similar ballistics .45 ACP rounds and spent $600 on a used S&W 625 to shoot them from and still saved money! Now for the $2-$3+/round prices of the .454/.460/.500 rounds, even at 'just' $2/round, by the time your 'free' gun shot the 470th round, you would start saving money with a 625JM you bought new for $760 (Local price here yesterday.) and shooting those 230gr FMJ .45 ACPs. Substitute a new 4" or 6" 629, the same $760, and .44 Magnum ammo that runs $30-$34/50 at discount houses, and you start saving money by the 559th round. Save money - buy a sensible caliber. Be happier - buy a better firearm.
Stainz
PS I owned - and shot - a .454 SRH for years. Carpal tunnel and arthritis have made my big bore enjoyment max out these days in the .44 Magnum area - plenty for me. Actually, my favorite homebrews are .44 Russians and Specials...