You may find the following website interesting/useful: Teaching with Original Historical Sources in Mathematics
Use of original historical sources in lower and upper division university courses is discussed. Reinhard Laubenbacher and David Pengelley were inspired by William Dunham to cover "mathematical masterpieces from the past, viewed as works of art." However, "Whereas Dunham presents his students with his own modern rendition of these masterpieces, [their] idea was to use the original texts themselves." They have authored at least two books intended for this purpose:
Mathematical Expeditions: Chronicles by the Explorers.
Mathematical Masterpieces: Further Chronicles by the Explorers
As I recall, the books use excerpts from the original sources, liberally augmented with modern explanation/analysis.
Assuming you are a student and not a mathematics researcher, my own personal opinion is that for a first reading it is better to use a (good) contemporary author writing for a student at roughly your level. He or she will have the benefit of history's digestion, simplification, and further development of the subject and, when applicable, will be able to translate outmoded notation into modern notation. If the original source is more recent and has been written at roughly your level then it may be superior. Otherwise, I think original sources are best for second readings and/or supplements.
Take a look at Keith Conrad's expository articles here https://kconrad.math.uconn.edu/blurbs/ on Galois Theory and algebraic number theory. They are all wonderful. In particular, he shows you how to compute stuff using the tools you learn which is very essential in my opinion. Most of the topics on Galois Theory covered in his notes seem relevant to algebraic number theory, but I haven't read all of them in detail because I learned Galois theory in a college course. There is a fair bit of elementary algebraic number theory (at the level of Samuels's book mentioned by lhf above) which you will need to be fairly comfortable with before you move on to to class field theory. I think Keith's notes on algebraic number theory covers this elementary material well, with many examples of computations. Finally, I highly recommend his note "The History of Class Field Theory". I am certain you will be adequately prepared to read Lang if you work through some of Conrad's material.
For algebraic number theory, I also recommend Cassels-Fröhlich's "Algebraic Number Theory" and Cox's "Primes of the form $x^2 + ny^2$". James Milne's notes on algebraic number theory and class field theory, freely available on his website, are great. The other standard reference is Neukirch's "Algebraic Number Theory" which I personally really like. When you read about valuations, completions etc., I recommend the handouts from Pete L. Clark's course available here: http://alpha.math.uga.edu/~pete/MATH8410.html. Also, highly recommended are Serre's "Local Fields" and Iwasawa's "Local Class Field Theory" (the latter is harder to find, but I have a pdf copy which I am willing to share with you). You see from this that there are many good choices, and you will have to choose your own poison.
I should mention that there are different approaches to class field theory (discussed in the following link: https://mathoverflow.net/questions/6932/learning-class-field-theory-local-or-global-first), and I learned local class field theory through Lubin-Tate formal groups. Their short paper on this topic is a wonderful read. Luckily, Prof. Lubin frequents MSE so he may be able to recommend more sources.
I think that if you want geometric motivation for commutative algebra, you will need some knowledge of algebraic geometry (at least at the level of classical varieties) and DonAntonio's suggestions are great. However, you can learn the required commutative algebra as and when you need it. Certainly books like Cassels-Fröhlich prove most of the results of commutative algebra used in algebraic number theory along the way.
If you want to learn commutative algebra as a subject in its own right, take a look at Eisenbud's "Commutative Algebra with a View Toward Algebraic Geometry" which motivates the algebraic constructions using geometry. However, as mentioned in the previous paragraph, you may need some basic knowledge of classical varieties to understand the geometric motivations in this book. For this, I recommend Karen Smith's "An Invitation to Algebraic Geometry". Also, there is this new gem A term of Commutative Algebra by Altman and Kleiman, which is like an Atiyah-Macdonald 2.0. In particular, the authors mention that their aim is to improve some of the exposition in Atiyah-Macdonald using categorical language. The notes are really wonderful.
Despite these recommendations, I don't think you need so much preparation to read Lang. In particular, I came across the various texts mentioned in my answer as and when I needed to learn a particular topic.
Best Answer
Take a look at Serge Lang's Basic Mathematics. It may be slightly more basic than you would probably like but it is nonetheless a great book. It is based on deriving and proving things from previously introduced concepts instead of just introducing things seemingly out of the blue and then spending several pages motivating the uses and talking endlessly about history. Surely there is some pedagogical method to it but it is aimed at people who find the topic interesting already and can appreciate the mathematics without seeing pictures of the space ship launch or elaborate 3d scenes involving cubes and spheres.
I would put it at a level somewhere between high school and college. I'm studying it right now but since I have very little true knowledge and understanding of mathematics from high school I find it a bit challenging in places, e.g. we never proved a thing in school so I had/have to learn how to go about proving things. I have learned so much about mathematics and proofs and how things really work, and I am only at the start of the book so there is quite a journey ahead of me!
Other books that may be of interest to you: Gelfand's Algebra, Method of coordinates, Functions and graphs, and Trigonometry. I've read some great things about them and I work through Algebra alongside Lang's text and I find them to complement each other fairly well. However, there is no coverage of complex numbers in this one. They are all very short and packed with great insight and challenging problems.