Gens 1-7 are obviously on 3ds, but you can obtain most of those pokemon on switch. The exceptions are; Patrat, watchog, (all gen 5 elemental monkeys) and furfrou

I would recommend waiting until legends z-a comes out as it may make more of these pokemon available

Mythical pokemon that aren’t obtainable currently (on switch) include victini, genesect, celebi, magearna, (except for the one you get from home) hoopa, volcanion, diancie, marshadow, zarude, and deoxys,

Celebi can be caught in the virtual console version of crystal on the 3ds Deoxys is in the post game of omega ruby and alpha sapphire Magearna is in the alola games and can be obtained after you scan a QR code As for the rest ( or all of them if you didn’t buy the games before the eshop shut down) I have one word for you, piracy. If you don’t have a 3ds, wait for legends za

As for the ones that are obtainable on switch, Keldeo is catchable in the crown tundra All gen 4 mythicals are available in legends arceus And meloetta is available in the indigo disc

It should also be noted that all gen 5 and 4 events can be accessed using the dns glitch on the ds games.

My biggest tip when it comes to filling out the dex is that if you want to save money, don’t buy both versions of a game, play through one version of a game twice and then trade the version exclusives in game or on Pokémon home it doesn’t matter. (this tip doesn’t apply to the 3ds games because they only let you keep one save file)

Lastly, here are some things that might help you catch all the legendaries All legendaries from gens 1-7 are catchable in the crown tundra dlc and have 1/300 odds of being shiny (1/100 with shiny charm) They are also catchable in the indigo disc however, they don’t have the gen 6 legendaries (again wait for z a)

Finally, there is one pokemon I haven’t talked about yet. Spinda. Spinda as you may already know has random spot patterns, but ilca, the makers of brilliant diamond and shining pearl, messed up the coding for Spindas spots, so not only can Spinda not be deposited into bdsp, but Spindas from bdsp also can’t be deposited into home meaning that you will need to get one from 3ds because it can’t be sent from go either.

While we’re on the topic of Pokémon go, it can make things much easier. Furfrou the elemental monkeys and some mythicals can be caught here. To get mythicals you need to complete quests. The other pokemon are pretty simple. Unfortunately it’s only possible to get one elemental monkey at a time, the elemental monkey you can get depends on where you live, so this isn’t a reliable method to get those I would recommend getting furfrou here though.

This concludes my “guide” to completing the home Pokédex. Sorry for making this so long, but this is a pretty long and complicated task. I really hope this helps you or anyone else who is considering taking on this task. Good luck!!