Well, let's put it this way.
If you are looking to collect cards with only the first 3 Generations of Pokemon, you want any set before DP. That's the EX, Neo, and Base blocks (as well as the recent set, Evolutions). HGSS sets were a gen 4 set, despite their namesake being a game based on Johto, so many of them were "tainted" (as the genwunners would say) with Sinnoh mons. As a side note, you also need to define "Johto and Hoenn pokemon", as pokemon like Yanmega and Gallade, while introduced in Gen 4, appear in later versions of the Johto and Hoenn regions' regional pokedexes.
Within the newer stuff, with the exception of Evolutions, there is a healthy mix of new and old friends. None of these sets, as a general rule, are any more or less biased against the Johto and Hoenn mons. There are a few exceptions here and there, Primal Clash focused more on Hoenn mons, but no good way to do it. So, if you are collecting old mons, you will have to buy old sets, which are becoming more and more rare.
Arceus only knows why anyone would insist on collecting only the first 3 generations in 2017 though.
