I'm not an expert, but this is something I've been doing too. I bought a shotgun a few months ago. And now I am looking into getting my CCW permit so that I am more comfortable with transporting a pistol. If you're going to be transporting a pistol around, look up laws in your state about the transportation of a firearm. Does your state allow open carry, etc. You don't want to get stuck in a bad position illegally carrying/transporting a firearm. But I'm also going to have to travel more with my pistol, which is why I'd be more comfortable with the CCW permit. But that's just me.
Things I purchased for my shotgun. I've bought a safe with quick access, ammo cans containers and dehumidifying gel silica packets for shotgun shells, gun cleaning kit, ear protection for practicing, gun case for transporting, 12 gauge #4 buckshot & lead and steel target loads. For within my safe I also bought a dehumidifying canister. Which is just something that you recharge by throwing in the oven every 6 months. This will keep your guns dry and prevent issues in the future, depending on where you're storing the safe and where you live etc. (I don't think I missed anything)
As for buying the shotgun, super easy. I bought it for self defense and maybe trap shooting. Took maybe an hour or two to walk out with a shotgun. I got a good deal on a Benelli nova for only 300 dollars. Pump action, simple.
But I've been looking at pistols for the past 3 months, and it looks like decent reliable ones are around 4-500 dollars. I've been looking specifically at getting a Glock. Since my pistol would also be for self defense, I want something reliable. I've learned really any of the generations of glocks are the same with minimal changes. Whatever is cheapest is the best one to pick.
Let me know if you have any questions.