Pool of Radiance is the single best game, but the Krynn trilogy overall is much better than the the quartet of games that starts with PoR. Also, the Gold Box engine was designed for low-level play, with hardly any alterations over the nine games that used it (not counting the two Buck Rogers games or the Unlimited Adventures: Fantasy Construction Kit), and tends to falter at representing higher-level D&D adventures. The ideal would be to start with PoR, then shift to the Krynn trilogy and play that to completion. If you haven't yet gotten tired of the Gold Box games, you could then import your party from PoR into Curse of the Azure Bonds and proceed from there.
If I play POR first, I'll be compelled to do the whole series of 4 games. I'll probably start with the savage frontiers duo.
If you start playing, remember that the class and race restrictions in AD&D 1st Edition were quite drastic. Back then, what we referred to as "demi-humans"—a term that would probably brand me as a Nazi in modern D&D—could typically only level up to 10 and had limited multiclassing options. The game was very much human-centric, as was its original intention.
This doesn't matter much at the beginning, but it can hurt you in the long term. In Krynn, however, these limitations are less noticeable and not as severe.
Only demihumans could multiclass, I think, and the restrictions were there because there were advantages to being an elf or a dwarf that sort of front-loaded their effectiveness. They got ability score bonuses (and some penalties) but also stuff like Elves being immune to sleep spells and having magic resistance, infravision, bonsues to hit with long swords and bows - Dwarves had darkvision, an attack bonus against orcs and other goblinoids, the ability to detect unusual "stonework," including secret doors and traps, a dodge bonus against giants, etc.
But also, as you say, Gygax in particular wanted D&D to be human-centric. In the original game, "Elf" was a class, you weren't a fighter or a magic user, you were an Elf and depending on your ability score you could only progress so far in level.
I read an article or blog post not long ago that suggested the better way to handle the advantages demihumans had would have been to require more XP to gain a level. But that's not the Gold Box solution. It's not a problem in PoR, but later on it becomes an issue.