PHB plus One

One of my great horrors in late-edition 3.5e (and also in Pathfinder) is that there's so much stuff that it's pretty hard to keep track of everything. Worse, there are a lot of exploits and broken combinations scattered throughout the books (though, it should be said, some of the worst offenders are right there in the first PHB - the single-classed Wizard pretty much blows everything else out of the water). This makes constructing characters a bit of a nightmare, and makes maintaining any sort of a balance in the game a real pain, too.

On the other hand, I'm not terribly keen on the notion of just declaring "core rules only" and banning all the supplements wholesale. (Although on the other other hand, I'm increasingly of the opinion that almost all RPGs run best with only those core rules, and indeed any game that needs, or "needs", supplemental material is frankly not very good anyway.)

With 5e, WotC's Adventurer's League programme have introduced a policy where PCs can be built according to a "PHB plus One" policy - you can use anything from the PHB, and then one other source. So if you want a race from "Volo's Guide" then that's fine, or if you want a spell from "Xanathar's Guide" that's fine, but you can't have both - one or the other.

Obviously, that applies some rather tight limits to the game, and cuts out on an awful lot of fun concepts... but on the other hand, it serves as a very neat way to cut down on the complexity and eliminate broken combinations (that largely don't exist in 5e anyway, but still).

That being the case, if I should run 3e again (and if I run D&D again, it's looking increasingly like being 3e), I suspect that I'll be adding a similar restriction to my house rules - PCs can be built using the PHB, the base 'setting' book (if any), and then one other sourcebook.

(Incidentally, and technically, the DMG and MM would be free as well - so if the character buys/crafts items, or summons monsters/polymorphs, the appropriate books could be referenced... but if they wanted to go beyond those core books then that would count as their "plus one".)