Small base dies
are for auto loading guns (usually gas operated). You don't need that with your Savage.
Full length sizing
is the standard, normal resizing dies, you need one.
die is optional, and you can full length resize everytime. Neck sizing keeps the brass closer to your guns chamber. Neck sized brass is only used in the exact same rifle as fired before.
Short base FL
Short Base FL. (2) I see Lee has a set of dies, what is the difference between Pacesetter and RGB series. (3) Difference between 2 die set -vs- 3 die set in .308. Is it better to have 3 dies?
(Full length) - never heard of.
is Lee's standard, They are good and worth the $3 extra.
Really Good Buy are about the same but do not come with the shellholder and dipper that Lee supplies with their other dies (worth the $3).
sets have 3 dies.
sets have two dies. Got it?
Now that we have the math straight, "standard" is FL Sizing Die and Bullet seating dies which also crimps. That is TWO dies.
You need to read the product descriptions carefully, but many add the neck sizing die as the Third die for rifle, but pistol dies may include a powder through neck expander, and/or a factory crimp die.