I haven't started to reload yet so still a noob.

I'm going to pickup a Redding National Match 3-Die Set .308 Win from a seller here. Do I still need to buy neck sizer bushings with this set?
http://www.midwayusa.com/product/589103/redding-national-match-3-die-set-308-winchester

Also I still don't understand what's the difference between these two dies? Does one set not need the neck sizer bushings?

http://www.midwayusa.com/product/423053/redding-type-s-bushing-3-die-neck-sizer-set-338-lapua-magnum?cm_vc=ProductFinding

Does this one not need the neck sizer bushings because it has that adjuster knob?
http://www.midwayusa.com/product/423070/redding-type-s-match-bushing-3-die-neck-sizer-set-338-lapua-magnum?cm_vc=ProductFinding

IMO, you will not need to buy neck bushing dies unless you plan on just neck sizing your cases to fire form the brass for a particular chamber.  The national die set has a FL sizing die.  Whether you want to FL size or neck size your brass is it's own debate.

http://www.massreloading.com/rifle_neck_sizing.html

"Neck Sizing Dies
Neck sizing is best accomplished with a neck sizing die.  This die is similar to a standard full-length sizing die except that the only part of the die that contacts the brass is the portion that resizes the neck.   The part of the die that would normally size the body and shoulder of the case is oversized so that it will not form those parts of the case. 

Like a full-length die, the neck sizing die has a combination expander ball/decapping pin.   The expander ball in a neck sizing die performs the same function as the one in a full-length sizing die: The body of the die intentionally undersizes the neck, while expander ball enlarges it from the inside as it's pulled out of the case.  his allows the die to provide a consistent inside neck diameter regardless of the thickness of the brass.   Unfortunately, repeatedly undersizing and expanding the neck can make it brittle due to work hardening.   Fortunately, there's another kind of neck sizing die called a bushing neck sizing die that can minimize work hardening.

A bushing neck sizing die features a separate replaceable bushing inside the die that controls the amount that the neck is sized.   Bushings are available in various diameters, allowing you to select one that will squeeze down the neck only enough to hold the bullet (ideally, 0.002" smaller than the bullet diameter).   The downside of using a neck bushing die is that multiple bushings are required for different case thicknesses.   In other words, when you change headstamps, you will have to change the bushing if one of the manufacturer's brass is thicker or thinner than the other."

OK so I should get this one in 338 Lapua to match the one I'm buying from you?

http://www.midwayusa.com/product/423070/redding-type-s-match-bushing-3-die-neck-sizer-set-338-lapua-magnum?cm_vc=ProductFinding

I am not familiar with 338 so I may be off base a little as I only have experience with .223 and .308.  The one you posted is a totally different type of die set than the one National Match.  You first need to decide what type of reloading process you want to do. 

This is my opinion of things to consider:

Are you going to be using different types of brass  -  FL size
Are you going to be using different rifles for this die set   -  FL size
Do you plan on measuring neck concentricity  -  neck size
Do you want to fire form your brass to match your chamber  -  neck size
would you prefer to load all the rounds to a FL size spec  -  FL size

IMO these are the positives of the different dies:

Gains of using a neck die is that it works the brass less, supposedly lengthening the life of your brass (dependent upon how "hot" your loads are)

Gains of using a FL size is that the brass can be used in numerous rifles and IMO ensures that it will load and eject (note that some semi-autos may need small base dies).  I tried fire forming with a prior die set with my R700 (sold now) and had a hard time closing the bolt a couple of times (could have been my fault) and decided to FL size everything from then on.  Never had an issue and accuracy was good for my standards.

I was told to go with the neck first and later I can get the full size after a few reloads. My Barrett 98b is not a full on precision rifle.

So these are fine? No bushings necessary?

Redding Type S Bushing Full Length Sizer (.338 Lapua)
http://www.midwayusa.com/product/782196/redding-type-s-bushing-full-length-sizer-die-338-lapua-magnum?cm_vc=ProductFinding

Redding Type S Bushing 3-Die Neck Sizer Set (.338 Lapua)
http://www.midwayusa.com/product/423053/redding-type-s-bushing-3-die-neck-sizer-set-338-lapua-magnum?cm_vc=ProductFinding

I would take the recommendation of someone that uses the same platform as you.  But, for semi autos I was under the expression that you are supposed to always FL size your brass.

Precision hand loading is all about consistency.
I tried neck sizing in my 6mm bench rest rifle. I don't anymore. I found that every time you reuse the brass, The bolt is harder to work. Then you have to bump the shoulder back or F/L size. So you really are losing consistency. I F/L size with a redding bushing die and have better consistent accuracy than neck sizing.

I use a bushing die because I can set the neck tension to my liking and I don't use an expander. I dont just screw my die down to the shell plate, I adjust it to push the shoulder back .0005. That's what works for me in my rifle.
The benchrest pro's get a custom die cut to match their chamber and they F/L size. They are the most anal of reloaders.
Also with case life, neck sizing will likely get you nothing as primer pockets will get loose with high pressure loads and annealing will keep your neck and soft. I imagine you will be using high end brass like lapua if you have the money to buy a rifle like that. You should anneal often. It extends brass life and improves consistency/accuracy.

Thats just my opinion.