Ralts (Gardevoir only)
Zubat & Sewaddle are also possible, since happiness shouldn't be too hard of a requirement.
That leaves us with the following Types to choose from:
Bug: Caterpie, Weedle, Venipede, Sewaddle
Dragon: Dratini, Bagon
Electric: Mareep, Shinx
Flying: Pidgey, Zubat, Hoppip, Starly
Grass: Hoppip, Sewaddle
Ground: Trapinch, Sandile
Normal: Pidgey, Starly
Poison: Weedle, Zubat, Venipede
Psychic: Ralts, Beldum, Solosis
Rock: Larvitar, Aron
Steel: Aron, Beldum, Klink
Since some Pokemon lose or gain typings through evolution, they aren't included in those types here. (For example: Larvitar and Pupitar are Ground types, but Tyranitar replaces it with Dark, so the evo line can neither be classified as Ground, nor as Dark)
Looking at this, Poison/Grass/Ground doesn't work. From our 3 Poison types, Weedle's and Venipede's Bug types neutralize their weakness to Ground and Zubat is completly immune to it, due to its Flying type.
Flying/Grass/Rock might do it, but the secondary types cause varying effectivnesses among the possible candidates...