That 'hammer looking thing' will be your best friend when you screw up and need to disassemble all those bad rounds you made. Trust me, I know.
Couple of suggestions.
1. Reloading is absurdly addictive. Don't be tempted to make 200 rounds before you even fire them. Make ten at a time, put them in a baggie with a brief description of the powder, charge weight and OAL. That way if/when they don't function right you'll only be out that ten. By all means try a few different loads, just don't go making hundreds until you see what works in YOUR gun.
2. Start with 45acp. Arguably the easiest round to reload for as no trimming is involved and placing that big fat bullet on the case couldn't be easier. Skip rifle and shotgun loads until you get someone to show you how.
3. Controversial, but consider using a Lee Factory Crimp Die. It'll make SURE all your rounds will fit the chamber. It can't compensate for bad OAL lengths, that is your responsibility.