First thing is that you can't evolve Pikachu into A-Raichu until the 6th gym i think, pretty late into the game. You'll have access to an Solrock pretty soon, actually, before the 2nd gym. Not kidding, Solrock is amazing, it carries so much battles thanks to Rock Polish, great attacks and Cosmic Power, give it a try, as it can fill the Psychic spot (it's part of an event in a house east of Sheridan Village). Also you'llhave access to an Eevee preeeeetty soon (help center, battle me again, you can give a try as soon as you get into the village, but it's a HARD battle, so better wait until the 2nd gym). i recommend evolving it into a Sylveon. Great bulk, great special attack, has access to misty terrain, it's amazing. Since you are pretty weak to ground attacks, you could try to catch a grass type to swap Buizel (it has redundant coverage, and it sucks). Roselia it's pretty good, even if it isn't a Roserade. Although you can get a Shiny Stone as soon as the 2nd gym, only if you're luck, though, 1/3 chance, believe, it's through one of the quests on the Help Center. Budew is obtained at the garden on East Gearen, daytime and clear weather, I think. Also, if you struggle with the 2nd gym leader, catch a Vivillon on Route 1. Great speed, and Compound Eyes is BROKEN, since it's basically guaranteed sleep, try to swap it with Nidorino, considering it's very useless until it evolves.
TL;DR: Your main team should look like this by the time you get into Sheridan (2nd gym):
Quilava
Sylveon
Roselia (Or Vaporeon)
Solrock
Vivillon
Loudred
On rotation:
Electrode
Nidorino
Pichu