You'll beat the first two gyms easily with bulbasaur.
Catch a dugtrio for the 3rd.
Erikas gym is full of poison types so a psychic works well. I like Mr. Mime because it can learn Thunderbolt and levels quickly.
Koga's gym is mostly full of psychic types despite being a poison gym so use whatever you want dugtrio/mr. mime will be good against the poison types though.
Same with Sabrina.
Dugtrio is strong against gym 7&8 but you should also get a water type vaporeon is convenient but lots work.
lorelei goes down to mr. mimes thunderbolt or venu's razer leaf
bruno/agatha both die fast to psychic
If you go out of your way to catch articuno it makes extremely short work of lance.
and pick a favourite for the 6th slot
Venusaur, Mr. Mime, Dugtrio, Vaporeon, Articuno = easy win
