Your Guide to 90%+ Breeding Pairs

I can lend you a pair to get the egg dex.

Let me see if I can get an egg from my death star voltorb and then I will take you up on that. Thanks. :)

I wanna breed horse so whitch 2 pokemon do i use.

Which horse do you mean? Ponyta, Rapidash, Blitzle, Zebstrika, Keldeo, Mudbray, Mudsdale, Galarian Ponyta, Galarian Rapidash, Glastrier, Spectrier or did you just mean Horsea and are forgetting to put the 'a' at the end of it? Rapidash is Ponytas evolution, so you need a male and female Ponyta for those two. Zebstrika is Blitzles evolution, so you need a male and female Blitzles for those two. Keldeo is a legendary, so it is not breedable. Mudsdale is Mudbrays evolution, so you need a male and female Mudbrays for those two. Galarian Rapidash is Galarian Ponytas evolution, so you need a male and female Galarian Ponytas for those two. Glastrier and Spectrier are legendaries, so they're not breedable. And if you actually meant Horsea, you need a male and female Horseas.

I have a bit of a dumb question... do Exclusive pairs make less eggs in general than canon Pokémon? I have a 95% Avaragon pair I've been breeding for months - both are level 100 at full happiness (total percentage is 114%), yet I barely get 3 eggs after 2000 interactions.

They do, unfortunately! All exclusive and variants are much harder to breed than normal canon 'mons

Vampiress, how many of those can you use a ditto in place of one of the pokemon in the pair? (the horse list you showed, which, by the way, never occurred to me to think of as horses. lol)

You can use ditto in place of any breedable mon but you won’t get the max percentage ^^

How or where can I get a male Gumairy to breed with my female?

There are several places in the trade shops to help find another gender to make a breeding pair. Exclusive/Variants breeding swap is a good place to go!