Mossbergs are purty darned nice.

Start simple. A revolver and a shotgun. I like the 870 because it is an affordable work horse. I like revolvers for those that are not going to make training a consistent ritual. I like S&W revolvers, but there are others out there that work just as well. I would recommend a barrel length of 4 inches to begin with. The length is going to make aiming and accuracy a lot easier and more pleasant to shoot, but if you are already experienced, then a shorter barrel length is going to make concealment seem easier. I like .38 with +P rounds. There are other calibers out there that can do considerably more damage (like the .357 or .44), but they also are considerably more to handle than the .38. I believe shot placement to be more important than caliber size for the most part.
Just my two cents.

I will say that currently I am equipped with daily carry a S&W 990L, transitioning to the S&W M&P .45 this week and carried the S&W 4043 (.40 caliber) for almost 15 years. I started out carrying the S&W Model 64 and to this day regret not buying it when I had the chance (Serial # BY9122, if anyone has it and wants to offer to sell it to me, LOL). I have always worked my "carry" around the gun. This means I usually carry the 4 inch barrel issued gun and (with a little thought and placement) probably 99% of the people I come into contact with never know I have a gun on me, wearing winter clothing or summer clothing. The other 1% just know me, LOL. I was often kidded by fellow LEO about my choice to carry the 4043 when off duty and many referred to it as a boat anchor. I just replied with that was fine with me, for when I run out of ammo, then I can bludgeon the perp until threat no longer existed. :grins wickedly:

I also have owned AMT, Beretta, Glock, Sig, S&W J-frames and a few others and recently planted myself with a Colt Officers Model 1911. Currently, my shotgun is an 870 and my deer rifle is in .270.

This was just my opinion, along with a little background of my experience. Always start simple, then move on from there when the comfort level leads you to do so.

Remington 870, 18 inch barrel, night sights w/ a lighted foreend.

Any Glock you like depending on your stature and whether you plan to carry concealed (per state laws of course).

Simple firearms with a long history of reliability and ease of repair and as quality firearms go reasonably priced.

If you don't plan to maintain and practice (should just scub the idea of firearms if you don't really) then switch the Glock to a good quality revolver.

Ok, thanks guys. I'm gonna have to get to our local gun store with a couple pages of suggestions in hand.