Hello, my name is Tony I would like to begin with the setup I have in my house, and then ask the question and what I would like to do. First off, in my front entry way of my home, it's approx. 6 years old, so fairly new. I have a set of 4 light switches on the wall, one of them controls outside garage lights, another controls entry ceiling lamp, another controls outside receptacle on wall, and another controls outside entry door lamp (flood light). So my plan is to add another light switch to the existing set of 4 light switches to make it 5 total, and with that new light switch I would like to add a receptacle right below that light switch approx. 3-4 feet drop down the wall near the floor to plug a little entry way lamp into. So with that new light switch I can control that receptacle right below it. So my question is how would I go about wiring all this together, and what way should I do it, I know what parts I'm going to need, well I would imagine I'm going to have to purchase a 5 gang electrical box, and remove the 4 gang one right? I greatly appreciate the help, thanks again.

You will need a tester to determine if you have a black hot wire that is always hot in one of the other switches, you will likely find all 4 are hot. Now you need to find a neutral and it will not be the wire coming off the other side of any of these switches, are there any other wires running through these boxes? If you have 4 blacks coming in and 4 whites (should be taped black at end) going out you probably will not have a neutral. Do some testing and come back with what you find. There are several electricians here who can help you further.

It is a lot? Of time and work, oh yeah money, to go to 5 Gang, I would leave it 4 gang.
Then use a Dual Slider Dimmer for 2 of the light switches, or a "Stacked" switch, I hate those. And prefer all single gang devices. Can the new Light and receptacle be switched with and existing switch?
If you need 5 Gang, Then Do it, I like single gang control, unless you had a light and fan, then they make a light/fan combo in single gang device.
They also make 2 light dimming in single device.