Welcome to the game.
This sub-forum may not be the best choice for the question. You could try the Hints, Cheats and Spoilers sub-forum and just be sure you explain you don't want any out right cheats and spoilers.
That said there's nothing wrong with the build you're suggesting so long as you understand a few points about the game. First FO:NV uses a Damage Threshold instead of a Armor Class system. What this means you have to do a certain amount of damage in order to punch through heavily armored characters and critters. For a shotgun each pellet in buckshot ammunition is calculated on an individual basis. For example if you have a Caravan Shot gun firing 7 pellets each doing 6 damage you'll get 42 points of damage done to an unarmored critter or character. But if they have a damage threshold of 5 only one 1 point of damage is done for each pellet so the damage drops pretty drastically from 42 points of damage to only 7 points. If the critter has a damage threshold of 10 you might not do any damage at all.
(Critters/ npcs with high DT include Death Claws and Giant Rad Scorpions each with DT of 15 as well a Legion Centurions, Brotherhood of Steel Paladins and NCR Heavy Troopers. Critters with no DT, making them ideal for shotguns, are Cazadors and Nightstalkers.)
There are two ways around this by selecting a level 6 perk called Shotgun Surgeon which bypasses 10 points of Damage Threshold and by converting your Buckshot ammunition into Slugs which do all their damage in one hit. To convert go to a Handloading bench and chose the break down option for your shotgun shells then you can use the materials salvaged to make Slugs. You need to have a certain level of Repair skill for the process. 20 guage for example you need to have 25 Repair.
One other trick that isn't always obvious involves the 12 guage Bean Bag rounds. These do Fatique damage that doesn't kill but ignores DT. What you do is use the Bean Bags to knock out the target and then switch to regular ammo to kill them while they're helpless on the ground. Bean Bags and Slugs are the one two punch for killing the boogy man of the game Deathclaws. But be aware robots can't be fatiqued so Bean bags will only do minor damage against them.
As far as explosives go this includes grenades, land mines and explosive launchers including Grenade Rifles and Missile Launchers. Flame throwers count as Energy Weapons. Plasma Grenades and mines count as Explosive skill weapons.
Explosive mines and grenades are a bit harder to to come by in FO:NV than in FO3 but there are still enough around to be useful in some pretty tough fights. The mines are all proximity detonated but aren't triggered by floating critters like Bloat Flies or Mister Hand/Gutsys.
Each explosive has a blast radius. Any other mine inside that blast radius will be detonated in turn. This means if you set a string of land mines too close together the whole string will be detonated when your victim hits the first one. Also if you're trying to use land mines to take out a group of enemies the first one to reach a land mine will be hit by the blast but the ones following him may still be out of range.
One trick for this situation is to lay a string of land mines down then disarm all but the last one in the line. The last one will trigger the others so hopefully you not only catch the first one in the group chasing you but the others behind him as well. Another trick to making sure your enemy will walk over the mine is to place them at pinch points between building and fences, firing a shot at them to get them to chase you then running behind cover so that they run into your kill zone.
Well hopefully this helps a bit.